Antigen-binding molecule promoting disappearance of antigens having plurality of biological activities

ABSTRACT

The present inventors newly discovered that even if an antigen-binding molecule inhibits in vitro some of the physiological activities of an antigen having two or more physiological activities without inhibiting the remaining physiological activities, the molecule can promote elimination of the antigen from blood (from serum or plasma) and as a result reduce the physiological activities in vivo, when the antigen-binding molecule is conferred with the properties: (i) of binding to human FcRn under an acidic pH range condition; (ii) of binding under a neutral pH range condition to human Fc receptor stronger than native human IgG, and (iii) that its antigen-binding activity alters according to the ion concentration.

TECHNICAL FIELD

The present invention relates to antigen-binding molecules that can promote antigen elimination from the blood (serum or plasma), and thereby reduce the in vivo physiological activities of the antigen which are difficult to inhibit in vitro due to multiple physiological activities of the antigen, and pharmaceutical compositions comprising as an active ingredient the antigen-binding molecules.

BACKGROUND ART

There are many known examples of diseases whose onset is caused by disruption of the balance of physiological activities maintained under healthy conditions, due to an excessively increased plasma level of a physiologically active substance (for example, a cytokine) relative to healthy conditions. A possible effective means of treating such diseases is to inhibit the physiological activity of the excessive physiologically active substance. For example, an antibody that binds to an antigen having physiological activity, and thereby neutralizes its physiological activity can be an effective therapeutic agent.

However, when an antigen has two or more physiological activities, normally a single type of neutralizing antibody can inhibit only one physiological activity. It is expected to be difficult for such an antibody to cure a disease caused by the above-described physiologically active substance.

Physiologically active substances that have two or more physiological activities include, for example, high mobility group box 1 (HMGB1). HMGB1 was identified as a member of the HMG family which is a nuclear protein that contributes to the stability of higher-order DNA structure by binding to the DNA. HMGB1 consists of 215 amino acids, and structurally it is composed of three main domains: HMG A box, HMG B box, and an acidic carboxyl-terminal domain. Normally, HMGB1 is present in cells as a DNA-binding protein. However, HMGB1 is released to the outside of inflammatory or necrotic cells through an active or passive mechanism. Released HMGB1 is known to activate a variety of cell surface receptors such as receptor for advanced glycation endproducts (RAGE), Toll-like receptor 4 (TLR4), and IL-1 receptor via binding to various substances such as DNAs, lipopolysaccharide (LPS), and interleukin (IL)-1β, and thereby transmit the signal into cells, which leads to induction of various inflammatory reactions (Non-patent Document 1). Furthermore, HMGB1 has been suggested to play an important role in the onset of sepsis, based on the fact that the blood level of HMGB1 was elevated in sepsis model mice administered with LPS and the mouse mortality rate was decreased by administration of a polyclonal antibody against HMGB1 (Non-patent Document 2). Patent Document 1 discloses preparation of several monoclonal antibodies with high affinity for HMGB1 and that they inhibited the binding of HMGB1 to RAGE or TLR4 and reduced the mortality rate of sepsis model mice. However, there is no description on the acquisition of antibodies that inhibit the HMGB1 activities towards both RAGE and TLR4, suggesting that it is difficult for a single type of antibody to inhibit multiple activities of HMGB1.

Antibodies (IgGs) bind to neonatal Fc receptor (FcRn), and have long plasma retention. The binding of IgG to FcRn is observed only under an acidic condition (pH 6.0), and it is hardly observed under the neutral condition (pH 7.4). Typically, IgG is nonspecifically incorporated into cells via endocytosis, and returns to the cell surface by binding to endosomal FcRn under the acidic condition in the endosome. Then, IgG dissociates from FcRn under the neutral condition in plasma. IgGs that do not bind to FcRn enter the lysosome and are degraded there. When the FcRn binding of an IgG under the acidic condition is eliminated by introducing mutations into its Fc region, the IgG is not recycled from the endosome to the plasma, and as a result the plasma retention of IgG is markedly impaired. For a method of improving the plasma retention of IgG, a method that improves the FcRn binding under acidic conditions has been reported. When the FcRn binding under acidic conditions is improved by introducing an amino acid substitution into an IgG Fc region, the efficiency of recycling from the endosome to the plasma is increased, resulting in an improvement of the plasma retention. Meanwhile, it has been reported that, when the FcRn binding under the neutral condition is enhanced, IgG does not dissociate from FcRn under the neutral condition in plasma even when it returns to the cell surface via binding to FcRn under the acidic condition in the endosome, and consequently the plasma retention remains unaltered or is rather worsened (Non-patent Documents 3 to 5).

Recently, antibodies that bind to antigens in a pH-dependent manner have been reported (Patent Document 2). The antibodies, which strongly bind to antigens under the plasma neutral condition and dissociate from the antigens under the endosomal acidic condition, after being dissociated from the antigen, become again capable of binding to antigens when recycled to the plasma via FcRn. Thus, a single antibody can bind to multiple antigens repeatedly. Plasma retention of an antigen is much shorter than that of an antibody which has the FcRn-mediated recycling mechanism. Therefore, when an antigen is bound to an antibody, the plasma retention of the antigen is normally prolonged, resulting in an increase of antigen concentration in the plasma. On the other hand, it has been reported that the above-described antibodies which bind to antigens in a pH-dependent manner promote antigen elimination from plasma as compared to typical antibodies because they dissociate from the antigens in the endosome during the FcRn-mediated recycling process (Patent Document 2). However, there is no known antibody engineering technique that further improves the above-described effect of promoting antigen elimination from plasma.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] WO1995/002187 -   [Patent Document 2] WO2009/125825

Non-Patent Documents

-   [Non-patent Document 1] Sims G P et al., Annu. Rev. Immunol. (2010)     28, 367-388. -   [Non-patent Document 2] Wang H et al., Science (1999) 285, 248-251. -   [Non-patent Document 3] Yeung Y A et al., J. Immunol. (2009) 182,     7663-71. -   [Non-patent Document 4] Datta-Mannan A et al., J. Biol. Chem. (2007)     282, 1709-17. -   [Non-patent Document 5] Dall'Acqua W F et al., J. Immunol. (2002)     169, 5171-80.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention was achieved in view of the above circumstances. An objective of the present invention is to provide antigen-binding molecules that can promote antigen elimination from the blood (serum or plasma) and thereby reduce in vivo the physiological activities of the antigen which are difficult to inhibit with a single type of antigen-binding molecule in vitro because the antigen has two or more physiological activities. Another objective of the present invention is to provide methods for producing the antigen-binding molecules and pharmaceutical compositions comprising the antigen-binding molecules as an active ingredient.

Means for Solving the Problems

The present inventors conducted dedicated studies. As a result, the present inventors newly revealed that an antigen-binding molecule that inhibits some of the physiological activities of antigens with two or more physiological activities but does not inhibit the remaining physiological activities in vitro can promote antigen elimination from blood (serum or plasma), and reduce the physiological activities in vivo, by conferring the antigen-binding molecule with the properties of:

-   -   (i) binding to human neonatal Fc receptor (FcRn) under an acidic         pH range condition;     -   (ii) binding to human FcRn and/or human Fcγ receptor more         strongly than native human IgG under a neutral pH range         condition; and     -   (iii) altering the antigen-binding activity according to the ion         concentration condition.

The present invention is based on the above findings, and specifically relates to:

[1] an antigen-binding molecule that reduces plasma antigen concentration, wherein the antigen-binding molecule has characteristics (1) to (6) below:

-   -   (1) the antigen-binding molecule comprises an antigen-binding         domain and at least one receptor-binding domain;     -   (2) under an acidic pH range condition, the receptor-binding         domain has human neonatal Fc Receptor (FcRn)-binding activity;     -   (3) under a neutral pH range condition, the human Fc         receptor-binding activity of the receptor-binding domain is         higher than human Fc receptor-binding activity of native human         IgG; (4) an antigen-binding activity of the antigen-binding         domain is altered according to the ion concentration condition;     -   (5) the antigen has two or more physiological activities; and     -   (6) one or more physiological activities of the antigen are         inhibited by binding of the antigen-binding molecule, while at         least one type of physiological activity of the antigen is         maintained:         [2] the antigen-binding molecule of [1], characterized in that         it inhibits the activity of an antigen to bind one or more types         of target molecules by binding to the antigen while allowing the         antigen to maintain the binding activity to at least one type of         target molecule;         [3] the antigen-binding molecule of [1] or [2], wherein the         reduction of plasma antigen concentration is due to the         promotion of antigen uptake into cells;         [4] the antigen-binding molecule of any one of [1] to [3],         characterized in that the decrease of antigen concentration in         plasma results in reduction of the physiological activity of the         antigen in vivo;         [5] the antigen-binding molecule of any one of [1] to [4],         wherein the antigen is high mobility group box 1 (HMGB1);         [6] the antigen-binding molecule of [5], which inhibits the         binding between HMGB1 and receptor for advanced glycation         endproducts (RAGE);         [7] the antigen-binding molecule of [5] or [6], which inhibits         the binding between HMGB1 and Toll-like receptor 4 (TLR4);         [8] the antigen-binding molecule of any one of [1] to [4],         wherein the antigen is connective tissue growth factor (CTGF);         [9] the antigen-binding molecule of any one of [1] to [8],         wherein the human Fc receptor is human FcRn;         [10] the antigen-binding molecule of [9], wherein the         receptor-binding domain comprises an Fc region in which at least         one amino acid in the IgG Fc region is altered;         [11] the antigen-binding molecule of [10], wherein the amino         acid alteration in the IgG Fc region is an alteration of at         least one amino acid selected from positions:         234, 235, 236, 237, 238, 239, 244, 245, 248, 249, 250, 251, 252,         253, 254, 255, 256, 257, 258, 260, 262, 265, 267, 270, 272, 274,         279, 280, 282, 283, 284, 285, 286, 288, 289, 293, 295, 297, 298,         303, 305, 307, 308, 309, 311, 312, 313, 314, 315, 316, 317, 318,         325, 326, 327, 328, 329, 330, 332, 334, 338, 339, 340, 341, 343,         345, 360, 361, 362, 375, 376, 377, 378, 380, 382, 384, 385, 386,         387, 389, 390, 391, 413, 422, 423, 424, 427, 428, 430, 431, 433,         434, 435, 436, 437, 438, 440, and 442 (EU numbering);         [12] the antigen-binding molecule of [11], wherein the amino         acid alteration in the IgG Fc region is at least one amino acid         alteration selected from the alterations: wherein according to         EU numbering,         the amino acid at position 234 is Arg;         the amino acid at position 235 is Gly, Lys, or Arg;         the amino acid at position 236 is Ala, Asp, Lys, or Arg;         the amino acid at position 237 is Lys, Met, or Arg;         the amino acid at position 238 is Ala, Asp, Lys, Leu, or Arg;         the amino acid at position 239 is Asp or Lys;         the amino acid at position 244 is Leu;         the amino acid at position 245 is Arg;         the amino acid at position 248 is Ile or Tyr;         the amino acid at position 249 is Pro;         the amino acid at position 250 is Ala, Glu, Phe, Ile, Met, Gln,         Ser, Val, Trp, Gly, His, Leu, Asn, or Tyr;         the amino acid at position 251 is Arg, Asp, Glu, or Leu;         the amino acid at position 252 is Phe, Ser, Thr, Trp, or Tyr;         the amino acid at position 253 is Val;         the amino acid at position 254 is Ala, Gly, His, Ile, Gln, Ser,         Val, or Thr;         the amino acid at position 255 is Ala, Asp, Phe, His, Ile, Lys,         Leu, Met, Asn, Gln, Arg, Gly, Ser, Trp, Tyr, or Glu;         the amino acid at position 256 is Ala, Asp, Glu, Arg, Asn, Pro,         Thr, Ser, or Gln;         the amino acid at position 257 is Ala, Gly, Ile, Leu, Met, Asn,         Ser, Thr, or Val;         the amino acid at position 258 is Asp or His;         the amino acid at position 260 is Ser;         the amino acid at position 262 is Leu;         the amino acid at position 265 is Ala;         the amino acid at position 267 is Met or Leu;         the amino acid at position 270 is Lys or Phe;         the amino acid at position 272 is Ala, Leu, or Arg;         the amino acid at position 274 is Ala;         the amino acid at position 279 is Leu, Ala, Asp, Gly, His, Met,         Asn, Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 280 is Ala, Gly, His, Lys, Asn, Gln,         Arg, Ser, Thr, or Glu;         the amino acid at position 282 is Ala or Asp;         the amino acid at position 283 is Ala, Asp, Phe, Gly, His, Ile,         Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 284 is Lys;         the amino acid at position 285 is Asn;         the amino acid at position 286 is Ala, Asp, Phe, Gly, His, Ile,         Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or Glu;         the amino acid at position 288 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Leu, Met, Asn, Pro, Gln, Arg, Val, Trp, Tyr, or Ser;         the amino acid at position 289 is His;         the amino acid at position 293 is Val;         the amino acid at position 295 is Met;         the amino acid at position 297 is Ala;         the amino acid at position 298 is Gly;         the amino acid at position 303 is Ala;         the amino acid at position 305 is Ala or Thr;         the amino acid at position 307 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr;         the amino acid at position 308 is Ala, Phe, Ile, Leu, Met, Pro,         Gln, or Thr;         the amino acid at position 309 is Ala, Asp, Glu, Pro, His, or         Arg;         the amino acid at position 311 is Ala, His, Glu, Lys, Leu, Met,         Ser, Val, Trp, or Ile;         the amino acid at position 312 is Ala, Asp, Pro, or His;         the amino acid at position 313 is Tyr or Phe;         the amino acid at position 314 is Ala, Leu, Lys, or Arg;         the amino acid at position 315 is Ala, Asp, Glu, Phe, Gly, Ile,         Lys, Leu, Met, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or His;         the amino acid at position 316 is Ala, Glu, Phe, His, Ile, Lys,         Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Asp;         the amino acid at position 317 is Ala or Pro;         the amino acid at position 318 is Asn or Thr;         the amino acid at position 325 is Ala, Gly, Met, Leu, Ile, or         Ser;         the amino acid at position 326 is Asp;         the amino acid at position 327 is Gly;         the amino acid at position 328 is Arg, Asp, Glu, or Tyr;         the amino acid at position 329 is Lys or Arg;         the amino acid at position 330 is Leu;         the amino acid at position 332 is Glu, Phe, His, Lys, Leu, Met,         Arg, Ser, Trp, or Val;         the amino acid at position 334 is Leu;         the amino acid at position 338 is Ala;         the amino acid at position 339 is Asn, Thr, or Trp;         the amino acid at position 340 is Ala;         the amino acid at position 341 is Pro;         the amino acid at position 343 is Glu, His, Lys, Gln, Arg, Thr,         or Tyr;         the amino acid at position 345 is Ala;         the amino acid at position 360 is His;         the amino acid at position 361 is Ala;         the amino acid at position 362 is Ala;         the amino acid at position 375 is Ala or Arg;         the amino acid at position 376 is Ala, Gly, Ile, Met, Pro, Thr,         or Val;         the amino acid at position 377 is Lys;         the amino acid at position 378 is Asp, Asn, or Val;         the amino acid at position 380 is Ala, Asn, Thr, or Ser;         the amino acid at position 382 is Ala, Phe, His, Ile, Lys, Leu,         Met, Asn, Gln, Arg, Ser, Thr, Trp, Tyr, or Val;         the amino acid at position 384 is Ala;         the amino acid at position 385 is Ala, Gly, Lys, Ser, Thr, Asp,         His, or Arg;         the amino acid at position 386 is Arg, Asp, Ile, Met, Ser, Thr,         Lys, or Pro;         the amino acid at position 387 is Ala, Arg, His, Pro, Ser, Thr,         or Glu;         the amino acid at position 389 is Ala, Asn, Pro, or Ser;         the amino acid at position 390 is Ala;         the amino acid at position 391 is Ala;         the amino acid at position 413 is Ala:         the amino acid at position 423 is Asn;         the amino acid at position 424 is Ala or Glu;         the amino acid at position 427 is Asn;         the amino acid at position 428 is Ala, Asp, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 430 is Ala, Phe, Gly, His, Ile, Lys,         Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr;         the amino acid at position 431 is His or Asn;         the amino acid at position 433 is Arg, Gln, His, Ile, Pro, Ser,         or Lys;         the amino acid at position 434 is Ala, Phe, Gly, Met, His, Ser,         Trp, or Tyr;         the amino acid at position 435 is Lys, Arg, or Asn;         the amino acid at position 436 is Ala, His, Ile, Leu, Glu, Phe,         Gly, Lys, Met, Asn, Arg, Ser, Thr, Trp, or Val;         the amino acid at position 437 is Arg;         the amino acid at position 438 is Lys, Leu, Thr, or Trp:         the amino acid at position 440 is Lys; and         the amino acid at position 442 is Lys;         [13] the antigen-binding molecule of any one of [10] to [12],         wherein the IgG Fc region is the Fc region of a nonhuman         animal-derived IgG;         [14] the antigen-binding molecule of any one of [10] to [12],         wherein the IgG Fc region is the Fc region of a human-derived         IgG;         [15] the antigen-binding molecule of any one of [1] to [8],         wherein the human Fc receptor is a human Fcγ receptor:         [16] the antigen-binding molecule of [15], wherein the         receptor-binding domain comprises an Fc region in which at least         one amino acid in the IgG Fc region is altered;         [17] the antigen-binding molecule of [16], wherein the amino         acid alteration in the IgG Fc region is an alteration of at         least one amino acid selected from positions:         221, 222, 223, 224, 225, 227, 228, 230, 231, 232, 233, 234, 235,         236, 237, 238, 239, 240, 241, 243, 244, 245, 246, 247, 249, 250,         251, 252, 254, 255, 256, 257, 258, 260, 262, 263, 264, 265, 266,         267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 278, 279, 280,         281, 282, 283, 284, 285, 286, 288, 290, 291, 292, 293, 294, 295,         296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 307, 308, 309,         311, 312, 313, 314, 315, 316, 317, 318, 320, 322, 323, 324, 325,         326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 339,         341, 343, 375, 376, 377, 378, 379, 380, 382, 385, 386, 387, 389,         392, 396, 421, 423, 427, 428, 429, 430, 431, 433, 434, 436, 438,         440; and 442 (EU numbering);         [18] the antigen-binding molecule of [17], wherein the amino         acid alteration in the IgG Fc region is at least one amino acid         alteration selected from the alterations: wherein, according to         EU numbering,         the amino acid at position 221 is Lys or Tyr;         the amino acid at position 222 is Phe, Trp, Glu, or Tyr;         the amino acid at position 223 is Phe, Trp, Glu, or Lys;         the amino acid at position 224 is Phe, Trp, Glu, or Tyr;         the amino acid at position 225 is Glu, Lys, or Trp;         the amino acid at position 227 is Glu, Gly, Lys, or Tyr;         the amino acid at position 228 is Glu, Gly, Lys, or Tyr;         the amino acid at position 230 is Ala, Glu, Gly, or Tyr;         the amino acid at position 231 is Glu, Gly, Lys, Pro, or Tyr;         the amino acid at position 232 is Glu, Gly, Lys, or Tyr;         the amino acid at position 233 is Ala, Asp, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 234 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 235 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 236 is Ala, Asp, Glu, Phe, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 237 is Ala, Asp, Glu, Phe, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 238 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 239 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr;         the amino acid at position 240 is Ala, Ile, Met, or Thr;         the amino acid at position 241 is Asp, Glu, Leu, Arg, Trp, or         Tyr;         the amino acid at position 243 is Leu, Glu, Leu, Gln, Arg, Trp,         or Tyr;         the amino acid at position 244 is His;         the amino acid at position 245 is Ala;         the amino acid at position 246 is Asp, Glu, His, or Tyr,         the amino acid at position 247 is Ala, Phe, Gly, His, Ile, Leu,         Met, Thr, Val, or Tyr;         the amino acid at position 249 is Glu, His, Gln, or Tyr;         the amino acid at position 250 is Glu or Gln;         the amino acid at position 251 is Phe;         the amino acid at position 254 is Phe, Met, or Tyr;         the amino acid at position 255 is Glu, Leu, or Tyr;         the amino acid at position 256 is Ala, Met, or Pro;         the amino acid at position 258 is Asp, Glu, His, Ser, or Tyr;         the amino acid at position 260 is Asp, Glu, His, or Tyr;         the amino acid at position 262 is Ala, Glu, Phe, Ile, or Thr;         the amino acid at position 263 is Ala, Ile, Met, or Thr;         the amino acid at position 264 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 265 is Ala, Glu, Leu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or         Tyr;         the amino acid at position 266 is Ala, Phe, Ile, Leu, Met, or         Thr;         the amino acid at position 267 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr;         the amino acid at position 268 is Ala, Asp, Glu, Phe, Gly, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, or Trp;         the amino acid at position 269 is Asp, Phe, Gly, His, Ile, Lys,         Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 270 is Glu, Phe, Gly, His, Ile, Leu,         Met, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 271 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 272 is Asp, Phe, Gly, His, Ile, Lys,         Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 273 is Phe or Ile;         the amino acid at position 274 is Asp, Glu, Phe, Gly, His, Ile,         Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 275 is Leu or Trp;         the amino acid at position 276 is Asp, Glu, Phe, Gly, His, Ile,         Leu, Met, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 278 is Asp, Glu Gly, His, Ile, Lys,         Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp;         the amino acid at position 279 is Ala;         the amino acid at position 280 is Ala, Gly, His, Lys, Leu, Pro,         Gln, Trp, or Tyr;         the amino acid at position 281 is Asp, Lys, Pro, or Tyr;         the amino acid at position 282 is Glu, Gly, Lys, Pro, or Tyr;         the amino acid at position 283 is Ala, Gly, His, Ile, Lys, Leu,         Met, Pro, Arg, or Tyr;         the amino acid at position 284 is Asp, Glu, Leu, Asn, Thr, or         Tyr;         the amino acid at position 285 is Asp, Glu, Lys, Gln, Trp, or         Tyr;         the amino acid at position 286 is Glu, Gly, Pro, or Tyr;         the amino acid at position 288 is Asn, Asp, Glu, or Tyr;         the amino acid at position 290 is Asp, Gly, His, Leu, Asn, Ser,         Thr, Trp, or Tyr;         the amino acid at position 291 is Asp, Glu, Gly, His, Ile, Gln,         or Thr;         the amino acid at position 292 is Ala, Asp, Glu, Pro, Thr, or         Tyr;         the amino acid at position 293 is Phe, Gly, His, Ile, Leu, Met,         Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 294 is Phe, Gly, His, Ile, Lys, Leu,         Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 295 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 296 is Ala, Asp, Glu, Gly, His, Ile,         Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, or Val;         the amino acid at position 297 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 298 is Ala, Asp, Glu, Phe, His, Ile,         Lys, Met, Asn, Gln, Arg, Thr, Val, Trp, or Tyr;         the amino acid at position 299 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr;         the amino acid at position 300 is Ala, Asp, Glu, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp;         the amino acid at position 301 is Asp, Glu, His, or Tyr;         the amino acid at position 302 is Ile;         the amino acid at position 303 is Asp, Gly, or Tyr;         the amino acid at position 304 is Asp, His, Leu, Asn, or Thr;         the amino acid at position 305 is Glu, Ile, Thr, or Tyr;         the amino acid at position 311 is Ala, Asp, Asn, Thr, Val or         Tyr;         the amino acid at position 313 is Phe;         the amino acid at position 315 is Leu;         the amino acid at position 317 is Glu or Gln;         the amino acid at position 318 is His, Leu, Asn, Pro, Gln, Arg,         Thr, Val, or Tyr;         the amino acid at position 320 is Asp, Phe, Gly, His, Ile, Leu,         Asn, Pro, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 322 is Ala, Asp, Phe, Gly, His, Ile,         Pro, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 323 is Ile, Leu, or Met;         the amino acid at position 324 is Asp, Phe, Gly, His, Ile, Leu,         Met, Pro, Arg, Thr, Val, Trp, or Tyr;         the amino acid at position 325 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 326 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 327 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Asn, Pro, Arg, Thr, Val, Trp, or Tyr;         the amino acid at position 328 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 329 is Asp, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 330 is Cys, Glu, Phe, Gly, His, Ile,         Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 331 is Asp, Phe, His, Ile, Leu, Met,         Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 332 is Ala, Asp, Glu, Phe, Gly, His,         Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 333 is Ala, Asp, Glu, Phe, Gly, His,         Ile, Lys, Leu, Met, Pro, Arg, Ser, Thr, Val, or Tyr;         the amino acid at position 334 is Ala, Glu, Phe, His, Ile, Leu,         Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 335 is Asp, Phe, Gly, His, Ile, Leu,         Met, Asn, Pro, Arg, Ser, Val, Trp, or Tyr;         the amino acid at position 336 is Glu, Lys, or Tyr;         the amino acid at position 337 is Asp, Glu, His, or Asn;         the amino acid at position 339 is Asp, Phe, Gly, Ile, Lys, Met,         Asn, Gln, Arg, Ser, or Thr;         the amino acid at position 376 is Ala or Val;         the amino acid at position 377 is Gly or Lys:         the amino acid at position 378 is Asp;         the amino acid at position 379 is Asn;         the amino acid at position 380 is Ala, Asn, or Ser;         the amino acid at position 382 is Ala or Ile;         the amino acid at position 385 is Glu;         the amino acid at position 392 is Thr;         the amino acid at position 396 is Asp, Glu, Phe, Ile, Lys, Leu,         Met, Gln, Arg, or Tyr;         the amino acid at position 421 is Lys;         the amino acid at position 427 is Asn;         the amino acid at position 428 is Phe or Leu;         the amino acid at position 429 is Met;         the amino acid at position 434 is Trp;         the amino acid at position 436 is Ile; and         the amino acid at position 440 is Gly, His, Ile, Leu, or Tyr;         [19] the antigen-binding molecule of any one of [16] to [18],         wherein the human Fcγ receptor is FcγRIa, FcγRIIa, FcγRIIb, or         FcγRIIIa;         [20] the antigen-binding molecule of [17], wherein the amino         acid alteration in the IgG Fc region is an alteration wherein         the amino acid at position 238 is Asp and the amino acid at         position 271 is Gly according to EU numbering;         [21] the antigen-binding molecule of [20], wherein the IgG Fc         region comprises an additional alteration of at least one amino         acid selected from positions:         233, 234, 237, 244, 245, 249, 250, 251, 252, 254, 255, 256, 257,         258, 260, 262, 264, 265, 266, 267, 268, 269, 270, 272, 279, 283,         285, 286, 288, 293, 296, 307, 308, 309, 311, 312, 314, 316, 317,         318, 326, 327, 330, 331, 332, 333, 339, 341, 343, 375, 376, 377,         378, 380, 382, 385, 386, 387, 389, 396, 423, 427, 428, 430, 431,         433, 434, 436, 438, 440, and 442 according to EU numbering;         [22] the antigen-binding molecule of [21], wherein the amino         acid alteration in the IgG Fc region is at least one amino acid         alteration selected from the alterations: wherein according to         EU numbering,         the amino acid at position 233 is Asp;         the amino acid at position 234 is Tyr;         the amino acid at position 237 is Asp;         the amino acid at position 264 is Ile;         the amino acid at position 265 is Glu;         the amino acid at position 266 is Phe, Met, or Leu;         the amino acid at position 267 is Ala, Glu, Gly, or Gln;         the amino acid at position 268 is Asp or Glu;         the amino acid at position 269 is Asp;         the amino acid at position 272 is Asp, Phe, Ile, Met, Asn, or         Gln;         the amino acid at position 296 is Asp;         the amino acid at position 326 is Ala or Asp;         the amino acid at position 327 is Gly;         the amino acid at position 330 is Lys or Arg;         the amino acid at position 331 is Ser;         the amino acid at position 332 is Thr,         the amino acid at position 333 is Thr, Lys, or Arg; and         the amino acid at position 396 is Asp, Glu, Phe, Ile, Lys, Leu,         Met, Gln, Arg, or Tyr;         [23] the antigen-binding molecule of any one of [20] to [22],         wherein the IgG Fc region comprises an additional alteration of         at least one amino acid selected from positions:         244, 245, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262,         270, 272, 279, 283, 285, 286, 288, 293, 307, 308, 309, 311, 312,         314, 316, 317, 318, 332, 339, 341, 343, 375, 376, 377, 378, 380,         382, 385, 386, 387, 389, 423, 427, 428, 430, 431, 433, 434, 436,         438, 440, and 442 (EU numbering);         [24] the antigen-binding molecule of [23], wherein the amino         acid alteration in the IgG Fc region is at least one amino acid         alteration selected from the alterations: wherein according to         EU numbering,         the amino acid at position 244 is Leu;         the amino acid at position 245 is Arg;         the amino acid at position 249 is Pro;         the amino acid at position 250 is Gln or Glu;         the amino acid at position 251 is Arg, Asp, Glu, or Leu;         the amino acid at position 252 is Phe, Ser, Thr, or Tyr;         the amino acid at position 254 is Ser or Thr;         the amino acid at position 255 is Arg, Gly, Ile, or Leu;         the amino acid at position 256 is Ala, Arg, Asn, Asp, Gln, Glu,         Pro, or Thr;         the amino acid at position 257 is Ala, Ile, Met, Asn, Ser, or         Val;         the amino acid at position 258 is Asp;         the amino acid at position 260 is Ser;         the amino acid at position 262 is Leu;         the amino acid at position 270 is Lys;         the amino acid at position 272 is Leu or Arg;         the amino acid at position 279 is Ala, Asp, Gly, His, Met, Asn,         Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 283 is Ala, Asp, Phe, Gly, His, Ile,         Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr;         the amino acid at position 285 is Asn;         the amino acid at position 286 is Phe;         the amino acid at position 288 is Asn or Pro;         the amino acid at position 293 is Val;         the amino acid at position 307 is Ala, Glu, Gln, or Met;         the amino acid at position 308 is Ile, Pro, or Thr;         the amino acid at position 309 is Pro,         the amino acid at position 311 is Ala, Glu, Ile, Lys, Leu, Met,         Ser, Val, or Trp;         the amino acid at position 312 is Ala, Asp, or Pro;         the amino acid at position 314 is Ala or Leu;         the amino acid at position 316 is Lys;         the amino acid at position 317 is Pro;         the amino acid at position 318 is Asn or Thr;         the amino acid at position 332 is Phe, His, Lys, Leu, Met, Arg,         Ser, or Trp;         the amino acid at position 339 is Asn, Thr, or Trp;         the amino acid at position 341 is Pro;         the amino acid at position 343 is Glu, His, Lys, Gln, Arg, Thr,         or Tyr;         the amino acid at position 375 is Arg;         the amino acid at position 376 is Gly, Ile, Met, Pro, Thr, or         Val;         the amino acid at position 377 is Lys;         the amino acid at position 378 is Asp, Asn, or Val;         the amino acid at position 380 is Ala, Asn, Ser, or Thr;         the amino acid at position 382 is Phe, His, Ile, Lys, Leu, Met,         Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr;         the amino acid at position 385 is Ala, Arg, Asp, Gly, His, Lys,         Ser, or Thr;         the amino acid at position 386 is Arg, Asp, Ile, Lys, Met, Pro,         Ser, or Thr;         the amino acid at position 387 is Ala, Arg, His, Pro, Ser, or         Thr;         the amino acid at position 389 is Asn, Pro, or Ser;         the amino acid at position 423 is Asn;         the amino acid at position 427 is Asn;         the amino acid at position 428 is Leu, Met, Phe, Ser, or Thr;         the amino acid at position 430 is Ala, Phe, Gly, His, Ile, Lys,         Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr;         the amino acid at position 431 is His or Asn;         the amino acid at position 433 is Arg, Gln, His, Ile, Lys, Pro,         or Ser;         the amino acid at position 434 is Ala, Gly, His, Phe, Ser, Trp,         or Tyr;         the amino acid at position 436 is Arg, Asn, His, Ile, Leu, Lys,         Met, or Thr;         the amino acid at position 438 is Lys, Leu, Thr, or Trp;         the amino acid at position 440 is Lys; and         the amino acid at position 442 is Lys;         [25] the antigen-binding molecule of any one of [16] to [24],         wherein the IgG Fc region is an Fc region of nonhuman         animal-derived IgG;         [26] the antigen-binding molecule of any one of [16] to [24],         wherein the IgG Fc region is an Fc region of human-derived IgG;         [27] the antigen-binding molecule of any one of [1] to [26],         wherein the ion concentration is a hydrogen-ion concentration         (pH) and the antigen-binding activity is lower under an acidic         pH range condition than under a neutral pH range condition;         [28] the antigen-binding molecule of [27], wherein the acidic pH         is endosomal pH;         [29] the antigen-binding molecule of [27] or [28], wherein the         neutral pH is plasma pH;         [30] the antigen-binding molecule of any one of [27] to [29],         wherein the acidic pH is pH 5.5 to 6.5 and the neutral pH is pH         7.0 to 8.0;         [31] the antigen-binding molecule of any one of [27] to [30],         wherein the ratio of antigen-binding activity under an acidic pH         range condition and a neutral pH range condition is 2 or more in         the value of KD (acidic pH)/KD (neutral pH);         [32] the antigen-binding molecule of any one of [27] to [31],         wherein at least one amino acid is substituted with histidine         and/or at least one histidine is inserted in the antigen-binding         domain;         [33] the antigen-binding molecule of any one of [27] to [32],         wherein additionally the antigen-binding activity is lower under         a low calcium ion concentration condition than under a high         calcium ion concentration condition;         [34] the antigen-binding molecule of any one of [1] to [26],         wherein the ion concentration is a calcium ion concentration and         the antigen-binding activity is lower under a low calcium ion         concentration condition than under a high calcium ion         concentration condition;         [35] the antigen-binding molecule of [33] or [34], wherein the         low calcium ion concentration is a calcium ion concentration in         the endosome;         [36] the antigen-binding molecule of any one of [33] to [35],         wherein the high calcium ion concentration is a calcium ion         concentration in the plasma;         [37] the antigen-binding molecule of any one of [33] to [36],         wherein the low calcium ion concentration is calcium ion         concentration of 0.1 μM to 30 μM, and the high calcium ion         concentration is calcium ion concentration of 100 μM to 10 mM;         [38] the antigen-binding molecule of any one of [33] to [37],         wherein the ratio of the antigen-binding activity under a low         calcium ion concentration condition and under a high calcium ion         concentration is 2 or more in the value of KD (low calcium ion         concentration)/KD (high calcium ion concentration);         [39] the antigen-binding molecule of any one of [1] to [38],         wherein the antigen-binding domain is obtained from a library;         [40] the antigen-binding molecule of any one of [1] to [39],         wherein the antigen-binding molecule is an antibody:         [41] the antigen-binding molecule of [40], wherein the antibody         is any one of a chimeric antibody, a humanized antibody, and a         human antibody;         [42] a pharmaceutical composition comprising as an active         ingredient the antigen-binding molecule of any one of [1] to         [41];         [43] the pharmaceutical composition of [42] for treating a         disease for which one of the causes is assumed to be the         antigen;         [44] the pharmaceutical composition of [43], wherein the antigen         is HMGB1;         [45] the pharmaceutical composition of [43] or [44], wherein the         disease is sepsis;         [46] the pharmaceutical composition of [43], wherein the antigen         is CTGF;         [47] the pharmaceutical composition of [43] or [46], wherein the         disease is fibrosis;         [48] a method for producing the antigen-binding molecule of         [11], which comprises the steps of;     -   (a) selecting an antigen having two or more physiological         activities;     -   (b) obtaining an antigen-binding domain;     -   (c) obtaining at least one receptor-binding domain;     -   (d) selecting a domain of which antigen-binding activity changes         according to the ion concentration condition from the         antigen-binding domain obtained in step (b);     -   (e) selecting from the receptor-binding domain obtained in step         (c), a domain that has human FcRn-binding activity under an         acidic pH range condition and of which binding activity to human         Fc receptor under a neutral pH range condition is higher than         the human Fc receptor-binding activity of native human IgG;     -   (f) preparing an antigen-binding molecule in which the         antigen-binding domain selected in step (d) is linked to the         receptor-binding domain selected in step (e); and     -   (g) selecting from the antigen-binding molecule prepared in step         (f), an antigen-binding molecule that inhibits one or more         physiological activities of the antigen by binding to the         antigen while allowing the antigen to maintain at least one type         of physiological activity;         [49] the method of [48], wherein step (b) is the step of         isolating a domain that binds to the antigen and then altering         at least one amino acid in the domain;         [50] the method of [48] or [49], wherein step (c) is the step of         isolating a domain that binds to human FcRn and then altering at         least one amino acid in the domain;         [51] the method of any one of [48] to [50], wherein step (f) is         the step of:         (f) constructing a polynucleotide wherein a polynucleotide         encoding the antigen-binding domain selected in step (d) is         linked to a polynucleotide encoding the receptor-binding domain         selected in step (e), and producing an antigen-binding molecule         wherein the antigen-binding domain selected in step (d) is         linked to the receptor-binding domain selected in step (e) by         using the constructed polynucleotide;         [52] the method of any one of [48] to [51], wherein step (g) is         the step of:         (g) selecting from the antigen-binding molecule prepared step         (f), an antigen-binding molecule that inhibits one or more         binding activities of the antigen to target molecules by binding         to the antigen while allowing the antigen to maintain at least         one type of binding activity to target molecules; and         [53] the method of any one of [48] to [52], wherein the human Fc         receptor is human FcRn or human Fcγ receptor.

The present invention also relates to:

[54] a method for decreasing a plasma antigen concentration by administering the antigen-binding molecule of any one of [1] to [41], or an antigen-binding molecule produced by the production method of any one of [48] to [53]; [55] a method for promoting an antigen uptake into a cell by administering the antigen-binding molecule of any one of [1] to [41], or an antigen-binding molecule produced by the production method of any one of [48] to [53]; [56] a method for reducing the physiological activity of an antigen in vivo by administering the antigen-binding molecule of any one of [1] to [41], or an antigen-binding molecule produced by the production method of any one of [48] to [53]; [57] the method of any one of [54] to [56], wherein the antigen-binding molecule is an antibody; [58] the method of [57], wherein the antibody is a chimeric antibody, humanized antibody, or human antibody: [59] an agent for treating a disease, which comprises as an active ingredient the antigen-binding molecule of any one of [1] to [41], or an antigen-binding molecule produced by the production method of any one of [48] to [53]; [60] the therapeutic agent of [59], wherein the antigen is HMGB1; [61] the therapeutic agent of [59] or [60], wherein the disease is sepsis; [62] the therapeutic agent of [59], wherein the antigen is CTGF; [63] the therapeutic agent of [59] or [62], wherein the disease is fibrosis; and [64] a kit for use in the method of any one of [54] to [58], which comprises the antigen-binding molecule of any one of [1] to [41], or an antigen-binding molecule produced by the production method of any one of [48] to [53].

The present invention further relates to:

[101] a method of screening for an antibody whose antigen-binding activity alters depending on condition, which comprises the steps of:

-   -   (a) preparing an antibody-producing cell;     -   (b) contacting the cell of (a) with an antigen under the first         condition;     -   (c) selecting from the cell of step (b) a cell to which a         predetermined amount of antigen or more is bound;     -   (d) exposing the cell of step (c) to the second condition; and     -   (e) selecting from the cell of step (d) a cell to which the         binding amount of antigen is decreased as compared to step (c);         [102] the method of [101], which comprises the steps of:     -   (a) preparing an antibody-producing cell;     -   (b) contacting an antigen with the cell of (a) under the first         condition;     -   (c) contacting an anti-IgG antibody with the cell of step (b);     -   (d) selecting from the cell of step (c) a cell to which a         predetermined amount of antigen or more is bound and a         predetermined amount of anti-IgG antibody or more is bound;     -   (e) exposing the cell of step (d) to the second condition; and     -   (f) selecting from the cell of step (e) a cell to which the         binding amount of antigen is decreased as compared to step (d);         [103] the method of [102], which comprises the steps of:     -   (a) preparing an antibody-producing cell;     -   (b) contacting an antigen with the cell of (a) under the first         condition;     -   (c) enriching a cell that is bound to an antigen from the cell         of step (b);     -   (d) contacting an anti-IgG antibody with the cell of step (c);     -   (e) selecting from the cell of step (d) a cell to which a         predetermined amount of antigen or more is bound and a         predetermined amount of anti-IgG antibody or more is bound;     -   (f) exposing the cell of step (e) to the second condition; and     -   (g) selecting from the cell of step (f) a cell to which the         binding amount of antigen is decreased as compared to step (e);         [104] the method of any one of [101] to [103], wherein the first         and second conditions are ion concentration conditions;         [105] the method of [104], wherein the first condition is a         neutral pH and the second condition is an acidic pH;         [106] the method of [104], wherein the first condition is a high         calcium ion concentration and the second condition is a low         calcium ion concentration;         [107] the method of [104], wherein the first condition is a         neutral pH and a high calcium ion concentration, and the second         condition is an acidic pH and a low calcium ion concentration;         [108] the method of [105] or [107], wherein the neutral pH is pH         7.0 to 8.0 and the acidic pH is pH 5.5 to 6.5;         [109] the method of any one of [106] to [108], wherein the high         calcium ion concentration is a calcium ion concentration of 100         μM to 10 mM, and the low calcium ion concentration is the same         as or lower than the high calcium ion concentration;         [110] the method of any one of [101] to [109], wherein the         antibody-producing cell is a cell collected from blood, spleen,         and/or lymph node;         [111] the method of any one of [101] to [110], wherein the         antibody-producing cell is a B cell;         [112] the method of [111], wherein the antibody-producing cell         is a rabbit B cell;         [113] the method of any one of [101] to [112], wherein the         antigen and/or anti-IgG antibody is fluorescently labeled;         [114] the method of any one of [101] to [113], wherein the step         of selecting a cell is carried out by using FACS; and         [115] the method of any one of [101] to [114], wherein the step         of enriching a cell is carried out by using MACS.

The present invention also relates to:

[a] methods for treating diseases for which one of the causes might be an antigen that has physiological activities, methods for reducing plasma antigen concentration, methods for promoting antigen uptake into cells, or methods for reducing the physiological activities of an antigen in vivo, which comprise the step of administering an antigen-binding molecule of the present invention; [b] therapeutic agents for diseases for which one of the causes might be an antigen that has physiological activities, agents for reducing plasma antigen concentration, agents for promoting antigen uptake into cells, or agents for reducing the physiological activities of an antigen in vivo, which comprise an antigen-binding molecule of the present invention as an active ingredient; [c] antigen-binding molecules of the present invention for use in methods for treating diseases for which one of the causes might be an antigen that has physiological activities, methods for reducing plasma antigen concentration, methods for promoting antigen uptake into cells, or methods for reducing the physiological activities of an antigen in vivo; [d] use of an antigen-binding molecule of the present invention in producing therapeutic agents for diseases for which one of the causes might be an antigen that has physiological activities, agents for reducing plasma antigen concentration, agents for promoting antigen uptake into cells, or agents for reducing the physiological activities of an antigen in vivo; and [e] processes for producing therapeutic agents for diseases for which one of the causes might be an antigen that has physiological activities, agents for reducing plasma antigen concentration, agents for promoting antigen uptake into cells, or agents for reducing the physiological activities of an antigen in vivo, which comprise the step of using an antigen-binding molecule of the present invention.

Examples of diseases include diseases for which one of the causes is HMGB1, CTGF, or IgE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a result of FACS sorting for B cells that produce anti-HMGB1 antibodies. (A) shows a result of the first sorting under a neutral pH and high calcium ion concentration condition. (B) shows a result of the second sorting under an acidic pH and low calcium ion concentration condition. Numbers (1, 2, and 3) in the diagram indicate gate numbers.

FIG. 2 presents plotted graphs of the HMGB1-binding activity of anti-HMGB1 antibodies. (A), (B), and (C) shows a result of plotting antibodies produced by B cells derived from Gate 1, Gate 2, and Gate 3 in FACS sorting, respectively.

FIG. 3 is a graph showing the number of antibodies whose antigen-binding ability does not depend on pH and/or calcium ion concentration (gray area), and the number of antibodies whose antigen-binding ability depends on pH and/or calcium ion concentration (black area) among antibodies produced by B cells derived from Gate 1, Gate 2, and Gate 3.

FIG. 4-1 is a diagram showing Biacore sensorgrams for anti-HMGB1 antibodies (HMG233-IgG1 and HMG236-IgG1) and human HMGB1.

FIG. 4-2 is a continuation diagram of FIG. 4-1. The diagram shows sensorgrams for anti-HMGB1 antibodies (HMG481-IgG1 and HMG487-IgG1) and human HMG1.

FIG. 5 is a graph showing a result of RAGE ELISA for anti-HMGB1 antibodies (HMG233, HMG236, HMG481, HMG487, and HMG446). The absorbance for each antibody is shown as a relative value to the absorbance of a control in the absence of antibody which is taken as 100.

FIG. 6 presents graphs showing a result of TLR4/MD-2 ELISA for anti-HMGB1 antibodies (HMG233, HMG236, HMG481, HMG487, and HMG446). The absorbance for each antibody is shown as a relative value to the absorbance of a control in the absence of antibody which is taken as 100.

FIG. 7 is a graph showing a time course of serum human HMGB1 concentration in normal mice.

FIG. 8 is a graph showing a time course of serum anti-human HMGB1 antibody concentration in normal mice.

FIG. 9 is a diagram showing that antigens can be eliminated from plasma by using antibodies that bind to target antigens in a pH-dependent manner and have FcRn-binding activity in a neutral pH range.

FIG. 10 is a diagram showing sensorgrams for 6RKE02-IgG1 to hsIL-6R at pH 7.4 and pH 6.0.

FIG. 11 is a graph showing a result of biological activity evaluation using BaF3 cells expressing human gp130 (BaF/gp130).

FIG. 12 shows a time course of plasma hsIL-6R concentration after antibody administration in an infusion test using normal mice.

FIG. 13 shows a protocol of in vivo drug efficacy test (Test 1) using normal mice and the SAA inhibitory effect (mean±SE) of antibody administration.

FIG. 14 is a diagram showing a protocol of in vivo drug efficacy test (Test 2) using normal mice and the SAA inhibitory effect (mean±SE) of antibody administration.

FIG. 15 shows a non-limiting action mechanism for the elimination of soluble antigen from plasma by administering an antibody that binds to an antigen in an ion concentration-dependent manner and whose Fcγ receptor binding is enhanced at a neutral pH as compared to existing neutralizing antibodies.

FIG. 16 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 which binds to human IL-6 receptor in a pH-dependent manner or H54/L28-IgG1.

FIG. 17 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 which binds to human IL-6 receptor in a pH-dependent manner, Fv4-IgG1-F760 which is an Fv4-IgG1 variant that lacks mouse FcγR binding, Fv4-IgG1-F1022 which is an Fv4-IgG1 variant with enhanced mouse FcγR binding, or Fv4-IgG1-Fuc which is an Fv4-IgG1 antibody with low fucose content.

FIG. 18 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 or antigen-binding molecules comprising as the heavy chain, VH3-IgG1-F1022 or VH3-IgG1-F1093 which is a VH3-IgG1-F1022 variant with improved FcRn binding in an acidic pH range.

FIG. 19 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 or antigen-binding molecules comprising as the heavy chain, VH3-IgG1-F1022 or VH3-IgG1-F1093 which is a VH3-IgG1-F1022 variant with improved FcRn binding in an acidic pH range.

FIG. 20 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087 which is an Fv4-IgG1 variant with enhanced mouse FcγR binding (in particular, enhanced mouse FcγRIIb binding and mouse FcγRIII binding), and Fv4-IgG1-F1182 which is an Fv4-IgG1 variant with enhanced mouse FcγR binding (in particular, enhanced mouse FcγRI binding and mouse FcγRIV binding).

FIG. 21 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087, and Fv4-IgG1-F1180 and Fv4-IgG1-F1412 which are Fv4-IgG1-F1087 variants with improved FcRn binding in an acidic pH range.

FIG. 22 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1182, and Fv4-IgG1-F1181 which is an Fv4-IgG1-F1182 variant with improved FcRn binding in an acidic pH range.

FIG. 23 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087, and Fv4-IgG1-F1180 and Fv4-IgG1-F1412 which are Fv4-IgG1-F1087 variants with improved FcRn binding in an acidic pH range.

FIG. 24 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1182, and Fv4-IgG1-F1181 which is an Fv4-IgG1-F1182 variant with improved FcRn binding in an acidic pH range.

FIG. 25 shows a time course of human IL-6 receptor concentration in the plasma of normal mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse FcγRIIb binding and mouse FcγRIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse FcγRIIb binding and mouse FcγRIII binding.

FIG. 26 shows a time course of human IL-6 receptor concentration in the plasma of FcγRIII-deficient mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse FcγRIIb binding and mouse FcγRIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse FcγRIIIb binding and mouse FcγRIII binding.

FIG. 27 shows a time course of human IL-6 receptor concentration in the plasma of Fc receptor γ chain-deficient mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse FcγRIIb binding and mouse FcγRIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse FcγRIIb binding and mouse FcγRIII binding.

FIG. 28 shows a time course of human IL-6 receptor concentration in the plasma of FcγRIIb-deficient mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse FcγRIIb binding and mouse FcγRIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse FcγRIIb binding and mouse FcγRIII binding.

FIG. 29 shows a result of evaluating the platelet aggregation ability of the omalizumab-G1d-v3/IgE immunocomplex by platelet aggregation assay using platelets derived from donors with FcγRIIa allotype (R/H).

FIG. 30 shows a result of evaluating the platelet aggregation ability of the omalizumab-G1d-v3/IgE immunocomplex by platelet aggregation assay using platelets derived from donors with FcγRIIa allotype (H/H).

FIG. 31 shows a result of assessing CD62p expression on the membrane surface of washed platelets. The black-filled area in the graph indicates a result of ADP stimulation after reaction with PBS. The area that is not filled in the graph indicates a result of ADP stimulation after reaction with the immunocomplex.

FIG. 32 shows a result of assessing the expression of active integrin on the membrane surface of washed platelets. The black-filled area in the graph indicates a result of ADP stimulation after reaction with PBS. The area that is not filled in the graph indicates a result of ADP stimulation after reaction with the immunocomplex.

FIG. 33 shows a graph in which the horizontal axis shows the relative value of FcγRIIb-binding activity of each PD variant, and the vertical axis shows the relative value of FcγRIIa type R-binding activity of each PD variant. The value for the amount of binding of each PD variant to each FcγR was divided by the value for the amount of binding of IL6R-F652 (SEQ ID NO: 162)/IL6R-L, which is a control antibody prior to introduction of the alteration (IL6R-F652 is an antibody heavy chain comprising an altered Fc with substitution of Pro at position 238 (EU numbering) with Asp), to each FcγR; and then the obtained value was multiplied by 100, and used as the relative binding activity value for each PD variant to each FcγR. The F652 plot in the figure shows the value for IL6R-F652/IL6R-L.

FIG. 34 shows a graph in which the vertical axis shows the relative value of FcγRIIb-binding activity of variants produced by introducing each alteration into GpH7-B3 (SEQ ID NO: 168)/GpL16-k0 (SEQ ID NO: 169) which does not have the P238D alteration, and the horizontal axis shows the relative value of FcγRIIb-binding activity of variants produced by introducing each alteration into IL6R-F652 (SEQ ID NO: 162)/IL6R-L which has the P238D alteration. The value for the amount of FcγRIIb binding of each variant was divided by the value for the amount of FcγRIIb binding of the pre-altered antibody; and then the obtained value was multiplied by 100, and used as the value of relative binding activity. Here, region A contains alterations that exhibit the effect of enhancing FcγRIIb binding in both cases where an alteration is introduced into GpH7-B3/GpL16-k0 which does not have P238D and where an alteration is introduced into IL6R-F652/IL6R-L which has P238D. Region B contains alterations that exhibit the effect of enhancing FcγRIIb binding when introduced into GpH7-B3/GpL16-k0 which does not have P238D, but do not exhibit the effect of enhancing FcγRIIIb binding when introduced into IL6R-F652/IL6R-L which has P238D.

FIG. 35 shows a crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex.

FIG. 36 shows an image of superimposing the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex and the model structure of the Fc (WT)/FcγRIIb extracellular region complex, with respect to the FcγRIIb extracellular region and the Fc CH2 domain A by the least squares fitting based on the Cα atom pair distances.

FIG. 37 shows comparison of the detailed structure around P238D after superimposing the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex and the model structure of the Fc (WT)/FcγRIIb extracellular region complex with respect to the only Fc CH2 domain A or the only Fc CH2 domain B by the least squares fitting based on the Cα atom pair distances.

FIG. 38 shows that a hydrogen bond can be found between the main chain of Gly at position 237 (EU numbering) in Fc CH2 domain A, and Tyr at position 160 in FcγRIIb in the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex.

FIG. 39 shows that an electrostatic interaction can be found between Asp at position 270 (EU numbering) in Fc CH2 domain B, and Arg at position 131 in FcγRIIb in the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex.

FIG. 40 shows a graph in which the horizontal axis shows the relative value of FcγRIIb-binding activity of each 2B variant, and the vertical axis shows the relative value of FcγRIIa type R-binding activity of each 2B variant. The value for the amount of binding of each 2B variant to each FcγR was divided by the value for the amount of binding of a control antibody prior to alteration (altered Fc with substitution of Pro at position 238 (EU numbering) with Asp) to each FcγR; and then the obtained value was multiplied by 100, and used as the value of relative binding activity of each 2B variant towards each FcγR.

FIG. 41 shows Glu at position 233 (EU numbering) in Fc Chain A and the surrounding residues in the extracellular region of FcγRIIb in the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex.

FIG. 42 shows Ala at position 330 (EU numbering) in Fc Chain A and the surrounding residues in the extracellular region of FcγRIIb in the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex.

FIG. 43 shows the structures of Pro at position 271 (EU numbering) of Fc Chain B after superimposing the crystal structures of the Fc (P238D)/FcγRIIb extracellular region complex and the Fc (WT)/FcγRIIIa extracellular region complex by the least squares fitting based on the Cα atom pair distances with respect to Fc Chain B.

FIG. 44 shows an image of the Fc (P208)/FcγRIIb extracellular region complex determined by X-ray crystal structure analysis. For each of the CH2 and CH3 domains in the Fc portion, those on the left side are referred to as domain A and those on the right side are referred to as domain B.

FIG. 45 shows comparison after superimposing the structures of Fc (P208)/FcγRIIb extracellular region complex and Fc (WT)/FcγRIa extracellular region complex (PDB code: 3RY6) determined by X-ray crystal structure analysis with respect to the CH2 domain A of the Fc portion by the least squares fitting based on the Cα atom pair distances. In the diagram, the structure drawn with heavy line shows the Fc (P208)/FcγRIIb extracellular region complex, while the structure drawn with thin line indicates the structure of Fc (WT)/FcγRIIa extracellular region complex. Only the CH2 domain A of the Fc portion is drawn for the Fc (WT)/FcγRIIa extracellular region complex.

FIG. 46 shows in the X-ray crystal structure of the Fc (P208)/FcγRIIb extracellular region complex, a detailed structure around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion, which forms a hydrogen bond with Tyr at position 160 in FcγRIIb at the main chain moiety.

FIG. 47 shows in the X-ray crystal structure of the Fc (P208)/FcγRIIb extracellular region complex, the structure of amino acid residues around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion, which forms a hydrogen bond with Tyr at position 160 in FcγRIIb at the main chain moiety.

FIG. 48 shows comparison around the loop at positions 266 to 271 (EU numbering) after superimposing the X-ray crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex shown in Reference Example 15 and the Fc (P208)/FcγRIIb extracellular region complex with respect to the CH2 domain B of the Fc portion by the least squares fitting based on the Cα atom pair distances. When compared to Fc (P238D), Fc (P208) has the H268D alteration at position 268 and the P271G alteration at position 271 (EU numbering) in the loop.

FIG. 49 is a diagram showing the structure around Ser239 in the CH2 domain B of the Fc portion in the X-ray crystal structure of the Fc (P208)/FcγRIIb extracellular region complex, along with the electron density determined by X-ray crystal structure analysis with 2Fo-Fc coefficient.

FIG. 50 shows comparison after superimposing the three-dimensional structures of the Fc (P208)/FcγRIIaR extracellular region complex and Fc (P208)/FcγRIIb extracellular region complex determined by X-ray crystal structure analysis by the least squares fitting based on the Cα atom pair distances.

FIG. 51 shows comparison around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion between the X-ray crystal structures of the Fc (P208)/FcγRIIaR extracellular region complex and the Fc (P208)/FcγRIIb extracellular region complex, along with the electron density determined by X-ray crystal structure analysis with 2Fo-Fc coefficient.

FIG. 52 shows comparison around Asp at position 237 (EU numbering) in the CH2 domain B of the Fc portion between the X-ray crystal structures of the Fc (P208)/FcγRIIaR extracellular region complex and the Fc (P208)/FcγRIIb extracellular region complex, along with the electron density determined by X-ray crystal structure analysis with 2Fo-Fc coefficient.

FIG. 53 shows comparison between the constant-region sequences of G1d and G4d. In the diagram, the amino acids boxed with thick-frame indicate positions with different amino acid residues between G1d and G4d.

FIG. 54 shows the structure of the heavy chain CDR3 of the 6RL#9 antibody Fab fragment determined by X-ray crystal structure analysis. (i) shows the crystal structure of the heavy chain CDR3 obtained under a crystallization condition in the presence of calcium ion. (ii) shows the crystal structure of the heavy chain CDR3 obtained under a crystallization condition in the absence of calcium ion.

FIG. 55 shows a time course of the plasma concentration of each antibody in normal mice administered with antibody H54/L28-IgG1, FH4-IgG1, or 6RL#9-IgG1.

FIG. 56 shows a time course of the plasma concentration of soluble human IL-6 receptor (hsIL-6R) in normal mice administered with antibody H54/L28-IgG1, FH4-IgG1, or 6RL#9-IgG1.

FIG. 57 shows ion-exchange chromatograms for an antibody having human Vk5-2 sequence and an antibody having h Vk5-2_L65 sequence which has an altered glycosylation sequence in the human Vk5-2 sequence. Solid line indicates a chromatogram for an antibody having human Vk5-2 sequence (heavy chain: CIM_H (SEQ ID NO: 67); light chain: hVk5-2 (SEQ ID NO: 57)); broken line indicates a chromatogram for an antibody having hVk5-2_L65 sequence (heavy chain: CIM_H (SEQ ID NO: 67); light chain: hVk5-2_L65 (SEQ ID NO: 70)).

FIG. 58A shows ion-exchange chromatograms for an antibody having LfVk1_Ca sequence (heavy chain: GC_H (SEQ ID NO: 55); light chain: LfVk1_Ca (SEQ ID NO: 83)) and an antibody having a sequence in which Asp (D) in the LfVk1_Ca sequence is substituted with Ala (A) after storage at 5° C. (solid line) or 50° C. (dotted line). After storage at 5° C., the highest peak in the chromatogram for each antibody is defined as a main peak, and the y axis of each ion-exchange chromatogram was normalized to the main peak. The graph shows a chromatogram for an antibody having LfVk1_Ca (SEQ ID NO: 83) as the light chain.

FIG. 58B shows a chromatogram for an antibody having LfVk1_Ca1 (SEQ ID NO: 85) as the light chain.

FIG. 58C shows a chromatogram for an antibody having LfVk1_Ca2 (SEQ ID NO: 86) as the light chain.

FIG. 58D shows a chromatogram for an antibody having LfVk1_Ca3 (SEQ ID NO: 87) as the light chain.

FIG. 59A shows ion-exchange chromatograms for an antibody having LfVk1_Ca sequence (heavy chain: GC_H (SEQ ID NO: 55); light chain: LfVk1_Ca (SEQ ID NO: 83)) and an antibody having LfVk1_Ca6 sequence (heavy chain: GC_H (SEQ ID NO: 55); light chain: LfVk1_Ca6 (SEQ ID NO: 88)) in which Asp (D) at position 30 (Kabat numbering) in the LfVk1_Ca sequence is substituted with Ser (S) after storage at 5° C. (solid line) or 50° C. (dotted line). After storage at 5° C., the highest peak in the chromatogram for each antibody is defined as a main peak, and the y axis of each ion-exchange chromatogram was normalized to the main peak. The graph shows a chromatogram for an antibody having LfVk1_Ca (SEQ ID NO: 83) as the light chain.

FIG. 59B shows a chromatogram for an antibody having LfVk1_Ca6 (SEQ ID NO: 88) as the light chain.

FIG. 60 shows the relationship between designed amino acid distribution (indicated with “Design”) and amino acid distribution for sequence information on 290 clones isolated from E. coli introduced with a gene library of antibodies that bind to antigens in a Ca-dependent manner (indicated with “Library”). The horizontal axis indicates amino acid position (Kabat numbering). The vertical axis indicates percentage in amino acid distribution.

FIG. 61 shows sensorgrams for anti-IL-6R antibody (tocilizumab), antibody 6RC1IgG_010, antibody 6RC1IgG_012, and antibody 6RC1IgG_019 under a high calcium ion concentration (1.2 mM) condition. The horizontal axis shows time, and the vertical axis shows RU value.

FIG. 62 shows sensorgrams for anti-IL-6R antibody (tocilizumab), antibody 6RC1IgG_010, antibody 6RC1IgG_012, and antibody 6RC1IgG_019 under a low calcium ion concentration (3 μM) condition. The horizontal axis shows time, and the vertical axis shows RU value.

FIG. 63 shows the relationship between designed amino acid distribution (indicated with “Design”) and amino acid distribution for sequence information on 132 clones isolated from E. coli introduced with a gene library of antibodies that bind to antigens in a pH-dependent manner (indicated with “Library”). The horizontal axis shows amino acid position (Kabat numbering). The vertical axis indicates percentage in amino acid distribution.

FIG. 64 shows sensorgrams for anti-IL-6R antibody (tocilizumab), antibody 6RpH#01, antibody 6RpH#02, and antibody 6RpH#03 at pH 7.4. The horizontal axis shows time, and the vertical axis shows RU value.

FIG. 65 shows sensorgrams for anti-IL-6R antibody (tocilizumab), antibody 6RpH#01, antibody 6RpH#02, and antibody 6RpH#03 at pH 6.0. The horizontal axis shows time, and the vertical axis shows RU value.

MODE FOR CARRYING OUT THE INVENTION

The present invention provides antigen-binding molecules that reduce a plasma antigen concentration, which have the properties of (1) to (6) below:

-   -   (1) the antigen-binding molecules have an antigen-binding         domain(s) and a receptor-binding domain(s);     -   (2) the receptor-binding domain(s) has human neonatal Fc         receptor (FcRn)-binding activity under an acidic pH range         condition;     -   (3) the human Fc receptor-binding activity of the         receptor-binding domain(s) is stronger than that of native human         IgG under a neutral pH range condition;     -   (4) the antigen-binding activity of the antigen-binding         domain(s) changes depending on the ion concentration condition,     -   (5) the antigen (as a binding target) has two or more         physiological activities, and     -   (6) binding of the antigen-binding molecule inhibits one or more         of the physiological activities of the antigen (as a binding         target), while at least one physiological activity is         maintained.

In the present invention, the physiological activity is a general term for activities that cause quantitative and/or qualitative changes/influence in the living organism, tissue, cell, protein, DNA. RNA, or such; and for example, the activity of regulating a biological function such as metabolism, growth, reproduction, maintenance of homeostasis, mental activity, and biological defense. More specifically, it includes activities of regulating cell proliferation and maturation, metabolism mediated by the endocrine system, signal transduction in the nervous system, blood circulation, wound healing, immune response, and cell migration. Physiological activity can be reworded as biological activity. A physiologically active substance refers to a substance with such physiological activities. Physiologically active substances exert their physiological activities by acting on specific molecules (target molecules) that constitute the living organism, and conferring certain change/influence. In the present invention, physiologically active substances are also referred to as antigens that have physiological activities. Physiologically active substances of the present invention may be any substances as long as they have physiological activities; but preferably, they are polypeptides and modified products thereof that have physiological activities (physiologically active peptides). Preferred target molecules for physiologically active substances to exert physiological activities are cell surface receptors and intracellular receptors. Physiologically active substances exert their physiological activities by binding to a specific receptor and transducing signals into cells. When physiologically active substances result from conversion of precursors without physiological activities into mature types that have physiological activities, enzymes responsible for such conversion are also included in the physiologically active substances of the present invention. In this case, target molecules are substrates (precursors) for the enzymes. Physiologically active substances may be substances produced by organisms (humans or nonhuman organisms) or artificially synthesized substances. Physiologically active substances that might be a cause of disease in organisms (preferably humans) are preferred in the present invention.

Examples of physiologically active peptides include cell growth factors including fibroblast growth factors (FGFs), transforming growth factors (TGFs), bone morphogenetic factors (BMPs), epidermal growth factors (EGFs), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and bone morphogenetic factor (BMP); cytokines including interferons (IFNs), interleukins (ILs), colony stimulation factors (CSFs), erythropoietin, and tumor necrosis factor (TNF); various hormones such as insulin and parathyroid hormone (PTH); enzymes including proteases such as matrix metalloproteinases (MMPs); and enzyme inhibitory factors such as TIMPs (tissue inhibitor of metalloproteases).

Physiologically active substances of the present invention are preferably physiologically active substances derived from mammals, especially preferably physiologically active substances derived from humans.

Physiologically active substances can be obtained, for example, by purifying from a living organism. Alternatively, physiologically active substances can be prepared by chemical synthesis. When physiologically active substances are physiologically active peptides, they can also be prepared as recombinant peptides by using genetic engineering techniques. Specifically, nucleic acids encoding physiologically active peptides can be synthesized based on amino acid sequences of the physiologically active peptides or nucleotide sequences encoding them, by gene cloning methods or nucleotide synthesis methods known to those skilled in the art. After the nucleic acids are inserted into known expression vectors to transform appropriate host cells, physiologically active peptides of interest can be purified from the host cells or culture supernatants by known methods. Such purification can be achieved by using multiple chromatographies such as typical ion chromatographies and affinity chromatographies once or several times in combination or alone. Furthermore, the physiologically active peptides may be prepared as partial peptides, which comprise a portion of a physiologically active peptide, or may be prepared as fusion peptides by fusing with different polypeptides such as peptide tags and Fc fragments, as long as they retain their original physiological activities. Fusion peptides can be prepared by fusing in frame genes encoding two or more desired polypeptide fragments and inserting the resulting fusion genes into expression vectors as described above (Sambrook J et al., Molecular Cloning 2^(nd) ed. (1989) 9.47-9.58, Cold Spring Harbor Lab. Press). Target molecules that bind to physiologically active substances can also be obtained by similar methods.

Regarding methods for assaying in vitro physiological activity, physiologically active substances and their target molecules are prepared, and then their in vitro physiological activity can be assayed using methods capable of detecting their binding, for example, ELISA, FACS, and Biacore. Alternatively, the physiological activities can be measured by detecting cellular changes (for example, changes in cell proliferation or morphology, and changes in gene or protein expression) after reacting physiologically active substances with receptor-expressing cells. Meanwhile, in vivo physiological activities can be measured by observing changes in animals (for example, changes associated with biological functions such as metabolism, growth, maintenance of homeostasis) after administering physiologically active substances to the animals.

In the present invention, “having two or more physiological activities” means that a physiologically active substance has the property of binding to two or more different target molecules. A physiologically active substance may bind directly to target molecules, or may bind indirectly to target molecules after binding to a substance other than the target molecules that promotes binding to the target molecules. A domain(s) responsible for target molecule binding exists in a physiologically active substance. It is preferable that there are multiple binding domains in a physiologically active substance corresponding to two or more different target molecules. In particular, it is preferable that the binding domains are located in the three-dimensional structure, at positions distant enough not to inhibit all the binding of the physiologically active substance to the target molecules at the same time when an antigen-binding molecule of the present invention binds to the physiologically active substance.

In the present invention, “having an activity” means that measured values are greater than the background value (or a measured value for a negative control) in a system capable of measuring the activity. For example, having a binding activity means that measured values are greater than the background value in a system capable of measuring binding activity such as ELISA, FACS, and Biacore. In the present invention, the ratio of a measured value to the background value is preferably twice or more, more preferably three times or more, still more preferably five times or more, and particularly preferably 10 times or more.

In the present invention, “inhibiting activity” means that values measured in a system capable of measuring the activity after adding a substance are lower than values measured before adding the substance (or the measured value when a negative control is added). For example, inhibiting binding activity means that values measured after adding a substance are lower than values measured before adding the substance in a system capable of measuring the binding activity such as ELISA, FACS, and Biacore. In the present invention, the ratio of a measured value after adding a substance to a measured value before adding the substance (or a measured value when adding a negative control) is preferably 80% or less, more preferably 50% or less, still more preferably 30% or less, and particularly preferably 10% or less.

In the present invention, “maintaining an activity” means that a measured value after adding a substance is 80% or more of a measured value before adding the substance (or a measured value when a negative control is added) in a system capable of measuring the activity. For example, maintaining a binding activity means that a measured value after adding a substance is 80% or more of a measured value before adding the substance in a system capable of measuring the binding activity such as ELISA, FACS, and Biacore. In the present invention, the ratio of a measured value after adding a substance to a measured value before adding the substance (or a measured value when a negative control is added) is preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more.

In the present invention, “reducing plasma antigen concentration” means that plasma antigen concentration when an antigen-binding molecule of the present invention is administered to a subject is lower compared to when a negative control is administered to a subject. The percentage of reduction is not particularly limited; however, the percentage is preferably 80% or less, more preferably 50% or less, still more preferably 30% or less, and most preferably 10% or less. Furthermore, in the present invention, “reducing antigen concentration in plasma” is reworded as “promoting antigen elimination from plasma (clearance)”, “shortening antigen retention time in plasma”, and “shortening antigen half-life in plasma”. Meanwhile, “in plasma” may also be “in serum”. Antigen-binding molecules provided by the present invention can be administered to subjects (a living organism) by, for example, intradermal, intravenous, intravitreal, subcutaneous, intraperitoneal, parenteral, or intramuscular injection. Subjects to which antigen-binding molecules of the present invention are administered are preferably animals, more preferably mammals, and still more preferably humans.

The reduction of antigen concentration may be achieved by promoting antigen uptake into cells. Meanwhile, the reduction of antigen concentration preferably results in a decrease of the physiological activity of the antigen in vivo, and particularly preferably results in a decrease of all the physiological activities of the antigen.

Antigen concentration can be measured by appropriately using methods known to those skilled in the art. When an antigen is a physiologically active peptide, the concentration of the physiologically active peptide in a sample of unknown concentration can be determined by preparing standard samples of known concentration and a system that can quantitatively determine their concentration (for example, ELISA or Biacore), and creating a standard curve that shows the relationship between measured values and respective concentrations. Samples include plasma from the living organism, cell culture media, and cell extracts.

In the present invention, antigen uptake into cells means that the antigen is incorporated into cells by endocytosis. Whether antigen uptake into cells is promoted can be assessed by, for example, testing whether the antigen concentration in the culture medium is decreased as compared to a control or whether the antigen concentration in cells is increased as compared to a control after the antigen is added to the cell culture medium. Promotion of antigen uptake into cells means promotion of antigen elimination from plasma in the living organism. Thus, whether antigen uptake into cells is promoted can be assessed by, for example, testing whether the antigen concentration in plasma is decreased as compared to a control after the antigen is administered to a living organism.

Antigen-binding molecules provided by the present invention are not particularly limited as long as they have the properties described in (1) to (6) above. However, they are preferably polypeptides having the property of binding specifically to an antigen, human FcRn, and human Fc receptor; and they are more preferably antibodies, and particularly preferably IgGs. Antibodies may be chimeric antibodies, humanized antibodies, human antibodies, and such. Antibodies may also be bispecific antibodies, antibody modification products to which various types of molecules are linked, polypeptides comprising antibody fragments, and such. The antigen-binding molecules provided by the present invention comprise an antigen-binding domain(s) and a receptor-binding domain(s). The above-described domain refers to constitutional units that can be divided in parts and isolated. The size of the domain is not particularly limited. Each domain comprises a polypeptide. The antigen-binding domain of the present invention is not particularly limited as long as it has the property of binding specifically to an antigen; however, preferred examples include antibodies and fragments thereof (variable region, Fab, F(ab′)2, Fv, CDR, etc.), antibody-like molecules referred to as scaffold (DARPins (WO2002/020565), Affibody (WO1995/001937), Avimer (WO2004/044011; WO2005/040229), Adnectin (WO2002/032925), etc.), and target molecules (receptors) and fragments thereof (soluble receptors), which bind to physiologically active substances. Particularly preferred examples include antibody variable regions. Meanwhile, receptor-binding domains of the present invention are not particularly limited as long as they have the property of binding specifically to human FcRn and/or human Fc receptor, however, preferred examples include antibodies (IgGs) and fragments thereof (the constant region, Fc, etc.), albumin and fragments thereof (domain 3), anti-FcRn antibody and fragments thereof (variable region, Fab, F(ab′)2, Fv, CDR, etc.), anti-FcRn antibody-like molecules (DARPins (WO2002/020565), Affibody (WO1995/001937), Avimer (WO2004/044011; WO2005/040229), Adnectin (WO2002/032925), etc.), and anti-FcRn peptides. More preferred examples include IgG Fc regions. Human Fc receptors of the present invention are not particularly limited as long as human IgG, in particular human IgG Fc region, binds to them; however, preferably they are human FcRn and human Fcγ receptors. IgGs may be derived from nonhuman animals or humans; however, IgGs are preferably human IgGs, particularly preferably human IgG1. As described below, it is preferable that the Fc region of the IgGs has amino acid alterations.

An antigen-binding molecule of the present invention may comprise at least one receptor-binding domain. For example, a single antigen-binding molecule may comprise one antigen-binding domain and one receptor-binding domain, or may comprise one antigen-binding domain and multiple receptor-binding domains. When a single antigen-binding molecule comprises multiple receptor-binding domains, all of the receptor-binding domains may bind to the same type of human Fc receptors, or each of the domains may bind to different types of human Fc receptors. On the other hand, since one of the requirements for antigen-binding molecules of the present invention to fulfill is to have human FcRn-binding activity, it is preferable that at least one receptor-binding domain comprised in an antigen-binding molecule of the present invention binds to human FcRn. Without particular limitation, embodiments where a single antigen-binding molecule comprises two receptor-binding domains include antigen-binding molecules of which two receptor-binding domains both bind to human FcRn, and antigen-binding molecules of which one of the receptor-binding domains binds to human FcRn and the other binds to human Fcγ receptor. Alternatively, when a single antigen-binding molecule comprises one receptor-binding domain, the receptor-binding domain may at least bind to human FcRn and may have the property that the single domain simultaneously binds to other types of human Fc receptors. Such receptor-binding domains include, for example, IgG Fc regions. IgG Fc regions have the property of binding to human FcRn and human Fcγ receptor.

Herein, native human IgG refers to naturally-occurring human IgG. It is desirable that a fucose-containing sugar chain is linked at position 297 (EU numbering) in the Fc region. As a native human IgG, naturally-occurring human IgG1, IgG2, IgG3, and IgG4 can be used. Preferred native human IgG is a naturally-occurring human IgG1. Whether a linked sugar chain is a fucose-containing sugar chain can be assessed, for example, by the method described below. Test human IgG is incubated with N-Glycosidase F (Roche diagnostics) to release its sugar chains (Weitzhandler et al., J. Pharma. Sciences (1994) 83(12): 1670-1675). Then, the reaction solution is deproteinated by reacting ethanol (Schenk et al., J. Clin. Investigation (2001) 108 (11): 1687-1695) and concentrated to dryness, followed by fluorescence labeling with 2-aminopyridin (Bigge et al., Anal. Biochem. (1995) 230 (2): 229-238). Solid extraction is performed using cellulose cartridge to remove the reagents, and the resulting fluorescently 2-AB-labeled sugar chains are analyzed by normal phase chromatography. Whether the sugar chain linked to the Fc region of the test human IgG is a fucose-containing sugar chain can be assessed by observing peaks detected in the chromatogram.

“Chimeric antibodies” are antibodies prepared by combining sequences derived from different animals. Specifically, the chimeric antibody includes, for example, antibodies having heavy and light chain variable (V) regions from a mouse antibody and heavy and light chain constant (C) regions from a human antibody.

“Humanized antibodies”, also referred to as reshaped human antibodies, are antibodies in which the complementarity determining regions (CDRs) of an antibody derived from a nonhuman mammal, for example, a mouse, are grafted into the CDRs of a human antibody. Methods for identifying CDRs are known (Kabat et al., Sequence of Proteins of Immunological Interest (1987), National Institute of Health, Bethesda, Md.; Chothia et al., Nature (1989) 342: 877). General genetic recombination technologies suitable for grafting CDRs are also known (see European Patent Application EP 125023; and WO96/02576).

“A bispecific antibody” refers to an antibody that has two variable regions in the same antibody molecule that recognize different epitopes. A bispecific antibody may be an antibody that recognizes two or more different antigens, or an antibody that recognizes two or more different epitopes on a same antigen.

Furthermore, polypeptides comprising antibody fragments include, for example. Fab fragments, F(ab′)2 fragments, scFvs (Nat Biotechnol. 2005 September; 23(9): 1126-36), domain antibodies (dAbs) (WO2004/058821; WO2003/002609), scFv-Fc (WO2005/037989), dAb-Fc, and Fc fusion proteins. When a molecule contains an Fc region, the Fc region can be used as the receptor-binding domain. The Fc region refers to a portion of the heavy chain constant region, which starts from the N terminus of the hinge region corresponding to the papain cleavage site in the antibody molecule and contains the hinge, and the CH2 and CH3 domains. The IgG Fc region refers to, for example, from cysteine at position 226 (EU numbering) up to the C terminus, or from proline at position 230 (EU numbering) up to the C terminus; but are not limited thereto. Without particular limitation, examples of the IgG Fc region include the Fc regions of human IgG1 (SEQ ID NO: 49), IgG2 (SEQ ID NO: 50), IgG3 (SEQ ID NO: 51), and IgG4 (SEQ ID NO: 52). The IgG Fc region is preferably the Fc region of human IgG1.

Antibody-like molecule (scaffolding molecule or scaffold molecule) is a general name for molecules that have a common backbone structure and the property of being able to specifically bind to an antigen (Current Opinion in Biotechnology 2006, 17: 653-658; Current Opinion in Biotechnology 2007, 18: 1-10; Current Opinion in Structural Biology 1997, 7: 463-469; Protein Science 2006, 15: 14-27). Antibody-like molecules include, for example, DARPins (WO2002/020565), affibody (WO1995/001937), avimer (WO2004/044011; WO2005/040229), and adnectin (WO2002/032925).

Antibodies may contain modified sugar chains. Antibodies with modified sugar chains include, for example, antibodies with modified glycosylation (WO99/54342), antibodies that are deficient in sugar chain-attached fucose (WO00/61739; WO02/31140; WO2006/067847; WO2006/067913), and antibodies having sugar chains with bisecting GlcNAc (WO02/79255).

The binding between an antigen and an antigen-binding molecule of the present invention, or between a target molecule and an antigen with physiological activities can be measured by using methods known to those skilled in the art such as ELISA, FACS, and Biacore. By setting the measurement condition to an extracellular condition or intracellular condition, differences in the binding activity under such conditions can be assessed. Furthermore, such methods can be combined with the above-described methods for measuring the physiological activity of physiologically active substances to assess whether the binding of an antigen-binding molecule of the present invention to an antigen with physiological activities inhibits the physiological activity/activities of the antigen or maintains the physiological activity/activities.

The present invention provides antigen-binding molecules characterized in that they inhibit one or more binding activities of an antigen to its target molecules by binding to the antigen while allowing the antigen to maintain the binding activity to at least one type of its target molecules. Specifically, it is preferable that one or more physiological activities of an antigen having two or more physiological activities are inhibited by binding of an antigen-binding molecule of the present invention to the antigen. Inhibiting one or more physiological activities (or, are inhibited) means inhibiting the activity of an antigen, which has binding activity to multiple target molecules, to bind to one or more types of its target molecules (or, are inhibited). Furthermore, when an antigen-binding molecule of the present invention binds to an antigen having two or more types of physiological activities, it is preferable that the antigen maintains at least one type of physiological activity among its physiological activities (or, at least one type of physiological activity is maintained). Maintaining at least one type of physiological activity (or is maintained) means that an antigen maintains its binding-activity to at least one type of the target molecules (or is maintained) among the binding activities of the antigen to multiple target molecules.

When an antigen with physiological activity that is present in excess in a living organism causes a disease, molecules, for example, neutralizing antibodies which inhibit the physiological activity by binding to the antigen, are expected to be useful in treating the disease. However, when the antigen has two or more types of physiological activities, neutralizing antibodies can inhibit only a single type of physiological activity. On the other hand, antigen-binding molecules of the present invention can ultimately reduce the in vivo physiological activities by promoting antigen elimination from blood (serum or plasma) even when the antigen maintains at least one type of physiological activity. Thus, the antigen-binding molecules of the present invention are very useful as compared to common neutralizing antibodies.

In the present invention, when a human Fc receptor is human FcRn, the receptor-binding domain of antigen-binding molecules is preferably an IgG Fc region, more preferably an Fc region variant in which at least one amino acid in the IgG Fc region is altered. The IgG may be derived from nonhuman animals or humans; however, the IgG is preferably human IgG (IgG1, IgG2, IgG3, or IgG4), and particularly preferably human IgG. Examples of amino acid alterations include amino acid substitution, insertion, and deletion; however, amino acid substitution is preferred. The number of amino acids to be altered is not particularly limited, and amino acids may be altered at only one site or at two or more sites. In such amino acid alteration, amino acids at any positions may be altered to any amino acids as long as the Fc region variant after alteration has human FcRn-binding activity under acidic and neutral pH range conditions, and the human FcRn-binding activity under a neutral pH range condition is greater than that of human IgG. It is known that in a living organism, generally the extracellular pH (for example, in plasma) is neutral and the intracellular pH (for example, in the endosome) is acidic. It is also known that the binding between IgG and FcRn is detected only under an acidic (intracellular) pH condition and is almost undetectable under a neutral (extracellular) pH condition. For the antigen-binding molecules of the present invention, acidic pH is preferably endosomal pH and neutral pH is preferably plasma pH.

If the receptor-binding domains of antigen-binding molecules provided by the present invention can be conferred with the property of having human FcRn-binding activity under intracellular and extracellular pH conditions and the property that the human FcRn-binding activity under an extracellular pH condition is stronger than that of human IgG, extracellularly antigen-bound antigen-binding molecules of the present invention bind to cell-surface FcRn and are internalized into cells, which results in promotion of antigen uptake into cells from the outside of the cells. When administered to a living organism, such antigen-binding molecules can reduce plasma antigen concentration and decrease the physiological activities of antigens in vivo. Thus, antigen-binding molecules provided by the present invention are useful.

Human FcRn is structurally similar to major histocompatibility complex (MHC) class I polypeptides, and shares 22 to 29% sequence identity with class I MHC molecules (Ghetie et al., Immunol. Today (1997) 18 (12), 592-598). FcRn is expressed as a heterodimer consisting of 2 microglobulin which is a soluble β chain (or light chain), and transmembrane α chain (or heavy chain). FcRn α chain comprises three extracellular domains (α1, α2, and α3). The α1 and α2 domains interact with the FcRn-binding domain of antibody Fc region (Raghavan et al., Immunity (1994) 1, 303-315).

The gene and amino acid sequences for human FcRn are registered under GenBank accession number NM_001136019 (SEQ ID NO: 16) and NP_001129491 (SEQ ID NO: 17), respectively. In addition to human, the gene and amino acid sequences for mouse FcRn are registered under GenBank accession number NM_010189 (SEQ ID NO: 18) and NP_034319 (SEQ ID NO: 19), respectively; the gene and amino acid sequences for rat FcRn are registered under GenBank accession number NM_033351 (SEQ ID NO: 20) and NP_203502 (SEQ ID NO: 21), respectively.

Human FcRn (SEQ ID NO: 17) forms a complex with human β2 microglobulin (SEQ ID NO: 38) in vivo. The complex of soluble human FcRn and β2 microglobulin can be produced using general recombination/expression methods. Such a soluble human FcRn/β2 microglobulin complex can be used to assess the binding activity of receptor-binding domains of the present invention. In the present invention, unless otherwise specified, human FcRn refers to a form capable of binding to receptor-binding domains of the present invention, and includes, for example, a complex of human FcRn and human β2 microglobulin.

Receptor-binding domains that bind to FcRn under a neutral pH range condition more strongly than native human IgG can be produced by altering the amino acids of human IgG Fc region. Examples of alteration include substitution, insertion, and deletion of one or more amino acids. Alternatively, it is possible to use an antigen-binding domain characterized in binding to FcRn as the receptor-binding domain. Whether the FcRn-binding activity of a receptor-binding domain is higher than that of the native human IgG Fc region can be appropriately assessed by the above-described methods.

In the present invention, the human FcRn-binding activity under an acidic pH range condition means the human FcRn-binding activity at pH 4.0 to pH 6.5, preferably at pH 5.0 to pH 6.5, more preferably at any of pH 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, and 6.5, and particularly preferably at pH 5.8 to pH 6.0 which is close to the pH of early endosome in vivo. Meanwhile, in the present invention, the human FcRn-binding activity under a neutral pH range condition refers to human FcRn-binding activity at pH 6.7 to pH 10.0, preferably at pH 7.0 to pH 9.0, more preferably at any of pH 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0, and particularly preferably at pH 7.4 which is close to the pH of plasma in vivo.

When the binding affinity between a receptor-binding domain and human FcRn is very low at pH 7.4 and is difficult to determine accurately, the pH can be 7.0 instead of pH 7.4. Regarding the measurement temperature, the binding affinity between a receptor-binding domain and human FcRn may be measured at any temperature between 10° C. and 50° C. The binding affinity between a receptor-binding domain and human FcRn is preferably determined at 15° C. to 40° C., more preferably at any temperature of 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, and 35° C. Without particular limitation, the 25° C. temperature is a preferred embodiment.

As a receptor-binding domain that binds to human FcRn, an IgG Fc region is altered preferably at sites including, for example, amino acids at positions 221 to 225, 227, 228, 230, 232, 233 to 241, 243 to 260, 262 to 272, 274, 276, 278 to 289, 291 to 320, 324 to 341, 343, 345, 360 to 362, 370, 375 to 378, 380, 382, 384 to 387, 389 to 391, 396, 413, 414, 416, 422, 423, 424, 426 to 438, 440, and 442 (EU numbering). More specifically, such alteration includes, for example, alteration of amino acids shown in Table 1. Such alteration can be used to enhance the human FcRn binding of an IgG Fc region under a neutral pH range condition.

TABLE 1 POSITION AMINO ACID ALTERATION 256 P 280 K 339 T 385 H 428 L 434 W, Y, F, A, H

Meanwhile, an example of alteration that can enhance the human FcRn binding under an acidic pH range condition as compared to native human IgG is shown in Table 2. From among such alterations, appropriate alterations that can also enhance the human FcRn binding under a neutral pH range condition can be selected and used in the present invention. In alteration of IgG Fc region, particularly preferred sites for alteration include, for example, amino acid(s) at position(s) 234, 235, 236, 237, 238, 239, 244, 245, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 260, 262, 265, 267, 270, 272, 274, 279, 280, 282, 283, 284, 285, 286, 288, 289, 293, 295, 297, 298, 303, 305, 307, 308, 309, 311, 312, 313, 314, 315, 316, 317, 318, 325, 326, 327, 328, 329, 330, 332, 334, 338, 339, 340, 341, 343, 345, 360, 361, 362, 375, 376, 377, 378, 380, 382, 384, 385, 386, 387, 389, 390, 391, 413, 422, 423, 424, 427, 428, 430, 431, 433, 434, 435, 436, 437, 438, 440, and 442 (EU numbering). Furthermore, preferred site(s) besides those described above include, for example:

amino acid(s) at position(s) 252, 254, 256, 309, 311, 315, 433, and/or 434 (EU numbering) and, in combination with those described above, amino acid(s) at position(s) 253, 310, 435, and/or 426 (EU numbering), which are described in WO1997/034631; amino acid(s) at position(s) 238, 252, 253, 254, 255, 256, 265, 272, 286, 288, 303, 305, 307, 309, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 386, 388, 400, 413, 415, 424, 433, 434, 435, 436, 439, and/or 447 (EU numbering), which are described in WO2000/042072; amino acid(s) at position(s) 251, 252, 254, 255, 256, 308, 309, 311, 312, 385, 386, 387, 389, 428, 433, 434, and/or 436 (EU numbering), which are described in WO2002/060919; amino acid(s) at position(s) 250, 314, and 428 (EU numbering), which are described in WO2004/092219; amino acid(s) at position(s) 238, 244, 245, 249, 252, 256, 257, 258, 260, 262, 270, 272, 279, 283, 285, 286, 288, 293, 307, 311, 312, 316, 317, 318, 332, 339, 341, 343, 375, 376, 377, 378, 380, 382, 423, 427, 430, 431, 434, 436, 438, 440, and/or 442 (EU numbering), which are described in WO2006/020114; and amino acid(s) at position(s) 251, 252, 307, 308, 378, 428, 430, 434, and/or 436 (EU numbering), which are described in WO2010/045193. At least one amino acid selected from the amino acids described above can be altered to increase the human FcRn-binding activity under a neutral pH range condition. The number of amino acids to be altered is not particularly limited, and amino acids may be altered at only one site or two or more sites.

TABLE 2 POSITION AMINO ACID ALTERATION 221 Y, K 222 Y 223 E, K 224 Y, E 225 E, K, W 227 K, E, G 228 Y, K, G 230 E, G 232 K 233 R, S, M, T, W, Y, G 234 H, R, E, I, V, F, D, Y, G 235 Y, V, N, S, T, Q, D 236 I, V, K, P, E, Q, H, W, Y, D, T, M, A, F, S, N, R 237 I, W, S, T, E, R, N, Q, K, H, D, P, L, M 238 A, L, D, S, T, H, W, V, I, G, M, F, E, K 239 M, R, T, G, V, E, D, L, A 240 I, M, T 241 E, W, L 243 E, W 244 L 245 R 246 Y, H 247 D 248 Y 249 P, Q, Y, H 250 L, E, Q 251 T, D 252 Y, W, Q 254 H 255 E, Y, H 256 A 257 A, I, M, N, S, V, T, L, Y, C 258 D, Y, H, A 259 I, F, N 260 S, D, E, H, Y 262 L, E 263 I 264 F, A, I, T, N, S, D 265 R, P, G, A 266 I 267 K, E, A 268 E, M 269 M, W, K, P, I, S, G, V, F, Y, A 270 K, S, I, A 271 A, V, S, Y, I, T 272 A, L, R, I, D, H, V, W, Y, P, T 274 M, F, G, E, I, T, N 276 D, F, H, R, L, V, W, A 278 R, S, V, M, N, I, L, D 279 A, D, G, H, M, N, Q, R, S, T, W, Y, C, I 281 D, Y 282 G, K, E, Y 283 A, D, F, G, H, I, K, L, N, P, Q, R, S, T, W, Y 284 T, L, Q, E 285 N, Y, W, Q, K, E, D, Y 286 F, L, Y, E, P, D, K, A 287 S, H 288 N, P, Y, H, D, I, V, C, E, G, L, Q, R 289 H 291 Q, H 292 Y, E, D 293 V 294 I, K, G 295 V, T 296 E, I, L 298 F, E, T, H 299 W, F, H, Y 300 K, A, G, V, M, Q, N, E 301 E 302 I 303 Y, E, A 304 N, T 305 A, H 306 Y 307 A, E, M, Q, Q, H 308 A, R, F, C, Y, W, N, H 311 A, I, K, L, M, V, W, T, H 312 A, P, H 315 T, H 316 K 317 A, P, H 318 N, T, R, L, Y 319 L, I, W, H, M, V, A 320 L, M, H, N 324 T, D 325 F, M, D 326 A 327 D, K, M, Y, H, L 328 G, A, W, R, F 329 K, R, W 330 G, W, V, P, H, F 331 L, F, Y 332 F, H, K, L, M, R, S, W, T, Q, E, Y, D, N, V 333 L, F, M, A 334 A 335 H, F, N, V, M, W, I, S, P, L 336 E, K 337 A 338 A 339 N, W 341 P 343 E, H, K, Q, R, T, Y 360 H, A 362 A 375 R 376 A, C, I, M, P, T, V 377 K 378 Q, D, N, W 380 A, N, S, T, Q, R, H 382 A, F, H, I, K, L, M, N, Q, R, S, T, V, W, Y 385 N, E 386 H 387 H, Q 414 A 423 N 424 A 426 H, L, V, R 427 N 428 F 429 Q 430 A, F, G, H, I, K, L, M, N, Q, R, S, T, V, Y 431 H, K 432 H 433 P 434 G, T, M, S 435 K 436 I, L, T 437 H 438 K, L, T, W 440 K 442 K

Meanwhile, receptor-binding domains that originally have human FcRn-binding activity under acidic pH range and neutral pH range conditions include, for example, an IgG Fc region, wherein amino acids of the Fc region are selected from:

according to EU numbering, the amino acid at position 234 which is Arg; the amino acid at position 235 which is Gly, Lys, or Arg; the amino acid at position 236 which is Ala, Asp, Lys, or Arg; the amino acid at position 237 which is Lys, Met, or Arg; the amino acid at position 238 which is Ala, Asp, Lys, Leu, or Arg; the amino acid at position 239 which is Asp or Lys; the amino acid at position 244 which is Leu; the amino acid at position 245 which is Arg; the amino acid at position 248 which is Ile or Tyr; the amino acid at position 249 which is Pro; the amino acid at position 250 which is Ala, Glu, Phe, Ile, Met, Gln, Ser, Val, Trp, Gly, His, Leu, Asn, or Tyr; the amino acid at position 251 which is Arg, Asp, Glu, or Leu; the amino acid at position 252 which is Phe, Ser, Thr, Trp, or Tyr; the amino acid at position 253 which is Val; the amino acid at position 254 which is Ala, Gly, His, Ile, Gln, Ser, Val, or Thr; the amino acid at position 255 which is Ala, Asp, Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Gly, Ser, Trp, Tyr, or Glu; the amino acid at position 256 which is Ala, Asp, Glu, Arg, Asn, Pro, Thr, Ser, or Gln; the amino acid at position 257 which is Ala, Gly, Ile, Leu, Met, Asn, Ser, Thr, or Val; the amino acid at position 258 which is Asp or His; the amino acid at position 260 which is Ser; the amino acid at position 262 which is Leu; the amino acid at position 265 which is Ala; the amino acid at position 267 which is Met or Leu; the amino acid at position 270 which is Lys or Phe; the amino acid at position 272 which is Ala, Leu, or Arg; the amino acid at position 274 which is Ala; the amino acid at position 279 which is Leu, Ala, Asp, Gly, His, Met, Asn, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 280 which is Ala, Gly, His, Lys, Asn, Gln, Arg, Ser, Thr, or Glu: the amino acid at position 282 which is Ala or Asp; the amino acid at position 283 which is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 284 which is Lys: the amino acid at position 285 which is Asn; the amino acid at position 286 which is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or Glu; the amino acid at position 288 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro. Gln, Arg, Val, Trp, Tyr, or Ser; the amino acid at position 289 which is His; the amino acid at position 293 which is Val; the amino acid at position 295 which is Met; the amino acid at position 297 which is Ala; the amino acid at position 298 which is Gly; the amino acid at position 303 which is Ala; the amino acid at position 305 which is Ala or Thr; the amino acid at position 307 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 308 which is Ala, Phe, Ile, Leu, Met, Pro, Gln, or Thr; the amino acid at position 309 which is Ala, Asp, Glu, Pro, His, or Arg; the amino acid at position 311 which is Ala, His, Glu, Lys, Leu, Met, Ser, Val, Trp, or Ile; the amino acid at position 312 which is Ala, Asp, Pro, or His; the amino acid at position 313 which is Tyr or Phe; the amino acid at position 314 which is Ala, Leu, Lys, or Arg; the amino acid at position 315 which is Ala, Asp, Glu, Phe, Gly, Ile, Lys, Leu, Met, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or His; the amino acid at position 316 which is Ala, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Asp; the amino acid at position 317 which is Ala or Pro; the amino acid at position 318 which is Asn or Thr; the amino acid at position 325 which is Ala, Gly, Met, Leu, Ile, or Ser; the amino acid at position 326 which is Asp; the amino acid at position 327 which is Gly; the amino acid at position 328 which is Arg, Asp, Glu, or Tyr; the amino acid at position 329 which is Lys or Arg; the amino acid at position 330 which is Leu; the amino acid at position 332 which is Glu, Phe, His, Lys, Leu, Met, Arg, Ser, Trp, or Val; the amino acid at position 334 which is Leu; the amino acid at position 338 which is Ala; the amino acid at position 339 which is Asn, Thr, or Trp; the amino acid at position 340 which is Ala; the amino acid at position 341 which is Pro; the amino acid at position 343 which is Glu, His, Lys, Gln, Arg, Thr, or Tyr; the amino acid at position 345 which is Ala; the amino acid at position 360 which is His; the amino acid at position 361 which is Ala; the amino acid at position 362 which is Ala; the amino acid at position 375 which is Ala or Arg; the amino acid at position 376 which is Ala, Gly, Ile, Met, Pro, Thr, or Val; the amino acid at position 377 which is Lys: the amino acid at position 378 which is Asp, Asn, or Val; the amino acid at position 380 which is Ala, Asn, Thr, or Ser; the amino acid at position 382 which is Ala, Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Trp, Tyr, or Val; the amino acid at position 384 which is Ala; the amino acid at position 385 which is Ala, Gly, Lys, Ser, Thr, Asp, His, or Arg; the amino acid at position 386 which is Arg, Asp, Ile, Met, Ser, Thr, Lys, or Pro; the amino acid at position 387 which is Ala, Arg, His, Pro, Ser, Thr, or Glu; the amino acid at position 389 which is Ala, Asn, Pro, or Ser; the amino acid at position 390 which is Ala; the amino acid at position 391 which is Ala; the amino acid at position 413 which is Ala; the amino acid at position 423 which is Asn; the amino acid at position 424 which is Ala or Glu; the amino acid at position 427 which is Asn; the amino acid at position 428 which is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 430 which is Ala, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 431 which is His or Asn; the amino acid at position 433 which is Arg, Gln, His, Ile, Pro, Ser, or Lys; the amino acid at position 434 which is Ala, Phe, Gly, Met, His, Ser, Trp, or Tyr; the amino acid at position 435 which is Lys, Arg, or Asn; the amino acid at position 436 which is Ala, His, Ile, Leu, Glu, Phe, Gly, Lys, Met, Asn, Arg, Ser, Thr, Trp, or Val; the amino acid at position 437 which is Arg; the amino acid at position 438 which is Lys, Leu, Thr, or Trp; the amino acid at position 440 which is Lys; and the amino acid at position 442 which is Lys.

Amino acid positions to be selected may be only one, or two or more positions. Combinations of amino acids of two or more positions include, for example, those described in Tables 3, 4-1 to 4-5, and 13-1 to 13-14.

TABLE 3 COMBINATION OF AMINO ACID ALTERATION M252Y/S254T/T256E M252Y/S254T/T256E/H433K/N434F/Y436H H433K/N434F/Y436H T307A/E380A T307A/E380A/N434H T307A/E380A/N434A N434H/N315H N434H/T289H N434H/T370A/E380A T250Q/M428L T250Q/N434A M252W/N434A M252Y/N434A T256A/N434A T256D/N434A T256E/N434A T256S/N434A P257I/Q311I T307A/N434A T307E/N434A T307Q/N434A V308P/N434A L309G/N434A Q311H/N434A Q311R/N434A N315D/N434A A378V/N434A E380S/N434A E382V/N434A S424E/N434A M428L/N434A N434A/Y436I T437Q/N434A T437R/N434A

TABLE 4-1 COMBINATION OF AMINO ACID ALTERATION L234I/L235D G236A/V308F/I332E G236R/L328R G236A/I332E/N434S S239E/V264I/A330Y/I332E S239E/V264I/I332E S239E/V264I/S298A/A330Y/I332E S239D/D265H/N297D/I332E S239D/E272Y/I332E S239D/E272S/I332E S239D/E272I/I332E S239D/N297D/I332E S239D/K326T/I332E S239Q/I332Q S239Q/I332N S239D/I332D S239D/I332E S239Q/I332E S239E/I332E F241W/F243W F241Y/F243Y/V262T/V264T F241W/F243W/V262A/V264A F241L/V262I F243L/V262I/V264W F243L/K288D/R292P/Y300L/V305I/P396L/H435K F243L/K288D/R292P/Y300L/H435K F243L/R292P/Y300L/V305I/P396L/H435K P245G/V308F T250I/V259I/V308F T250I/V308F T250I/V308F/N434S T250Q/V308F/M428L T250Q/M428L L251I/N434S L251N/N434S L251F/N434S L251V/N434S L251M/N434S T252L/T254S/T256F M252Y/S254T/T256E/N434M M252Y/S254T/T256E/M428L/N434S M252Y/S254T/T256E M252Y/S254T/T256E/V308F M252Y/S254T/T256E/N434S M252Y/S254T/T256E/N434A M252Y/S254T/T256E/M428L M252Y/S254T/T256E/T307Q M252F/T256D M252Y/T256Q M252Y/P257L M252Y/P257N M252Y/V259I M252Y/V279Q M252Y/V308P/N434Y M252Q/V308F M252Y/V308F

Table 4-2 is a continuation table of Table 4-1.

TABLE 4-2 M252Q/V308F/N434S M252Y/V308F/M428L M252Y/V308F/N434M M252Y/V308F/N434S M252Y/Y319I M252Q/M428L/N434S M252Y/M428L M252Y/N434M M252Y/N434S M252Y/N434A M252Y/N434Y S254T/V308F R255H/N434A R255Q/N434S R255H/N434S T256V/V308F T256P/Q311I T256P/I332E T256P/I332F/S440Y T256P/E430Q T256P/N434H T256E/N434Y T256P/S440Y P257Y/V279Q P257L/V279E P257N/V279Q P257N/V279E P257N/V279Y P257L/V279Q P257N/{circumflex over ( )}281S P257L/{circumflex over ( )}281S P257N/V284F P257N/L306Y P257L/V308Y P257L/V308F P257N/V308Y P257I/Q311I/N434H P257L/Q311V P257L/G385N P257L/M428L P257I/E430Q P257I/N434H P257L/N434Y E758H/N434A E258H/N434H V259I/T307Q/V308F V259I/V308F V259I/V308F/Y319L V259I/V308F/Y319I V259A/V308F V259I/V308F/N434M V259I/V308F/N434S V259I/V308F/M428L/N434S V259I/V308F/M428L V259I/Y319I V259I/Y319I/M434S V259I/M428L V259I/M428L/N434S V259I/N434S

Table 4-3 is a continuation table of Table 4-2.

TABLE 4-3 V259I/N434Y V264I/A330L/I332E V264I/I332E D265F/N297E/I332E S267L/A327S E272R/V279L V279E/V284E V279Q/L306Y V279Y/V308F V279Q/V308F V279Q/G385H $$281S/V308Y $$281S/V308F $$281S/N434Y E283F/V284E V284E/V308F V284E/G385H K288A/N434A K288D/H435K K288V/H435D T289H/N434A T289H/N434H L306I/V308F T307P/V308F T307Q/V308F/N434S T307Q/V308F/Y319L T307S/V308F T307Q/V308F T307A/E310A/N434A T307Q/E380A/N434A T307Q/M428L T307Q/N434M T307I/N434S T307V/N434S T307Q/N434S T307Q/N434Y V308T/L309P/Q311S V308F/L309Y V308F/Q311V V308F/Y319F V308F/Y319I/N434M V308F/Y319I V308F/Y319L V308F/Y319I/M428L V308F/Y319I/M428L/N434S V308F/V319L/N434S V308F/I332E V308F/G385H V308F/M428L/N434M V308F/M428L V308F/M428L/N434S V308P/N434Y V308F/N434M V308F/N434S V308F/N434Y Q311G/N434S Q311D/N434S Q311E/M434S Q311N/N434S

Table 4-4 is a continuation table of Table 4-3.

TABLE 4-4 Q311Y/N434S Q311F/N434S Q311W/N434S Q311A/N434S Q311K/N434S Q311T/N434S Q311R/N434S Q311L/N434S Q311M/N434S Q311V/N434S Q311I/N434S Q311A/N434Y D312H/N434A D312H/N434H L314Q/N434S L314V/N434S L314M/N434S L314F/N434S L314I/N434S N315H/N434A N315H/N434N Y319I/V308F Y319I/M428L Y319I/M428L/N434S Y319I/N434M Y319I/N434S L328H/I332E L328N/I332E L328E/I332E L328I/I332E L328Q/I332E L328D/I332E L328R/M428L/N434S A330L/I332E A330Y/I322E I332E/D376V I332E/N434S P343R/E345D C376V/E430Q D376V/E430R D376V/N434H E380A/N434A G385R/Q386T/P387R/N389P G385D/Q386P/N389S N414F/Y416H M428L/N434M M428L/N434S M428L/N434A M428L/N434Y H429N/N434S E430D/N434S E430T/N434S E430S/N434S E430A/N434S E430F/N434S F430Q/N434S E430L/N434S E430I/N434S A431T/N434S Table 4-5 is a continuation table of Table 4-4.

TABLE 4-5 A431S/N434S A431G/N434S A431V/N434S A431N/N434S A431F/N434S A431H/N434S L432F/N434S L432N/N434S L432Q/N434S L432H/N434S L432G/N434S L432I/N434S L432V/N434S L432A/N434S H433K/N434F H433L/N434S H433M/N434S H433A/N434S H433V/N434S H433K/N434S H433S/N434S H433P/N434S N434S/M428L N434S/Y436D N434S/Y436Q N434S/Y436M N434S/Y436G N434S/Y436E N434S/Y436F N434S/Y436T N434S/Y436R N434S/Y436S N434S/Y436H N434S/Y436K N434S/Y436L N434S/Y436V N434S/Y436W N434S/Y436I N434S/T437I

Herein, higher human FcRn-binding activity than that of native human IgG means that the human FcRn-binding activity is, for example, 105% or more, preferably 110% or higher, 115% or higher, 120% or higher, 125% or higher, particularly preferably 130% or higher, 135% or higher, 140% or higher, 145% or higher, 150% or higher, 155% or higher, 160% or higher, 165% or higher, 170% or higher, 175% or higher, 180% or higher, 185% or higher, 190% or higher, 195% or higher, twice or higher, 2.5 fold or higher, 3 fold or higher, 3.5 fold or higher, 4 fold or higher, 4.5 fold or higher, 5 fold or higher, 7.5 fold or higher, 10 fold or higher, 20 fold or higher, 30 fold or higher, 40 fold or higher, 50 fold or higher, 60 fold or higher, 70 fold or higher, 80 fold or higher, 90 fold or higher, 100 fold or higher than that of native human IgG.

Such amino acid alterations can be appropriately introduced using known methods. For example, alterations in the Fc domain of human IgG1 are described in Drug Metab Dispos. 2007 January 35(1): 86-94; Int Immunol. 2006 Dec. 18, (12): 1759-69; J Biol Chem. 2001 Mar. 2, 276(9): 6591-604; J Biol Chem. (2007) 282(3): 1709-17; J Immunol. (2002) 169(9): 5171-80; J Immunol. (2009) 182(12): 7663-71; Molecular Cell, Vol. 7, 867-877, April, 2001; Nat Biotechnol. 1997 Jul. 15, (7): 637-40; Nat Biotechnol. 2005 Oct. 23, (10): 1283-8; Proc Natl Acad Sci USA. 2006 Dec. 5, 103(49): 18709-14; EP 2154157; US 20070141052; WO2000/042072; WO2002/060919; WO2006/020114; WO2006/031370; WO2010/033279; WO2006/053301; and WO2009/086320.

According to Yeung et al. (The Journal of Immunology, 2009 182: 7663-7671), the human FcRn-binding activity of human IgG1 is KD 1.7 μM under an acidic pH range (pH6.0) condition but is almost undetectable under a neutral pH range condition. Thus, preferred embodiments of antigen-binding molecules provided by the present invention include antigen-binding molecules of which human FcRn-binding activity under an acidic pH range condition is KD 20 μM or stronger and of which human FcRn-binding activity under a neutral pH range condition is comparable to or higher than that of human IgG. More preferred embodiments include antigen-binding molecules of which human FcRn-binding activity under an acidic pH range condition is KD 2.0 μM or stronger and of which human FcRn-binding activity under a neutral pH range condition is KD 40 μM or stronger. Still more preferred embodiments include antigen-binding molecules of which human FcRn-binding activity under an acidic pH range condition is KD 0.5 μM or stronger and of which human FcRn-binding activity under a neutral pH range condition is KD 15 μM or stronger. The above KD values refers to values determined by the method described in The Journal of Immunology, 2009 182: 7663-7671 (antigen-binding molecules are immobilized onto a chip, and human FcRn is injected as an analyte).

In a preferred embodiment, the antigen-binding molecules provided by the present invention have human FcRn-binding activity at pH 7.0 and at 25° C. which is stronger than human IgG. In a more preferred embodiment, human FcRn-binding activity at pH 7.0 and at 25° C. is 28-fold stronger than human IgG or stronger than KD 3.2 μM. In a more preferred embodiment, human FcRn-binding activity at pH 7.0 and at 25° C. is 38-fold stronger than human IgG or stronger than KD 2.3 μM.

KD (dissociation constant) can be used as a value for human FcRn-binding activity. However, the human FcRn-binding activity of human IgG is almost undetectable under a neutral pH range (pH 7.4) condition, and it is difficult to calculate the activity as KD. A method for assessing whether the human FcRn-binding activity at pH 7.4 is higher than that of human IgG is to assess based on the level of binding response in Biacore when analytes are injected at the same concentration. Specifically, if the response level when human FcRn is injected into a chip immobilized with an antigen-binding molecule provided by the present invention is greater than the response level when human FcRn is injected into a human IgG-immobilized chip, the human FcRn-binding activity of the antigen-binding molecule is concluded to be higher than that of the human IgG.

Fcγ receptor (FcγR) refers to a receptor capable of binding to the Fc region of IgGs (for example, IgG1, IgG2, IgG3, or IgG4), and practically includes any members belonging to the Fcγ receptor family. In human, the family includes FcγRI (CD64) including isoforms FcγRIa, FcγRIb and FcγRIc; FcγRII (CD32) including isoforms FcγRIIa (including allotype H131 and R131), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CD16) including isoform FcγRIIIa (including allotype V158 and F158) and FcγRIIIb (including allotype FcγRIIIb-NA1 and FcγRIIIb-NA2); as well as all unidentified human FcγRs, FcγR isoforms, and allotypes thereof. However, Fcγ receptor is not limited to these examples. Without being limited thereto, origin of FcγR includes humans, mice, rats, rabbits, and monkeys. FcγR may be derived from any organisms. Mouse FcγR includes, without being limited to, FcγRI (CD64), Fcγ-RII (CD32), FcγRIII (CD16), and FcγRIII-2 (FcγRIV, CD16-2), as well as all unidentified mouse FcγRs, FcγR isoforms, and allotypes thereof. Such preferred Fcγ receptors include, for example, human FcγRI (CD64), FcγRIIa (CD32), FcγRIIb (CD32), FcγRIIIa (CD16), and/or FcγRIIIb (CD16). The polynucleotide sequence and amino acid sequence of human FcγRI are shown in SEQ ID NOs: 39 (NM_000566.3) and 40 (NP_000557.1), respectively; the polynucleotide sequence and amino acid sequence of human FcγRIIa (allotype H31) are shown in SEQ ID NOs: 41 (BC020823.1) and 42 (AAH20823.1) (allotype R131 is a sequence in which amino acid at position 166 of SEQ ID NO: 42 is substituted with Arg), respectively; the polynucleotide sequence and amino acid sequence of FcγIIb are shown in SEQ ID NOs: 43 (BC146678.1) and 44 (AAI46679.1), respectively; the polynucleotide sequence and amino acid sequence of FcγRIIIa are shown in SEQ ID NOs: 45 (BC033678.1) and 46 (AAH33678.1), respectively; and the polynucleotide sequence and amino acid sequence of FcγRIIIb are shown in SEQ ID NOs: 47 (BC128562.1) and 48 (AAI28563.1), respectively (RefSeq accession number is shown in each parentheses). Whether an Fcγ receptor has binding activity to the Fc region of an IgG can be assessed by ALPHA screen (Amplified Luminescent Proximity Homogeneous Assay), surface plasmon resonance (SPR)-based BIACORE method, and others (Proc. Natl. Acad. Sci. USA (2006) 103(11), 4005-4010), in addition to FACS and ELISA.

Meanwhile, “Fc ligand” or “effector ligand” refers to a molecule and preferably a polypeptide that binds to an antibody Fc region, forming a complex. The molecule may be derived from any organisms. The binding of an Fc ligand to Fc region preferably induces one or more effector functions. Such Fc ligands include, but are not limited to, Fc receptors, FcγR, FcαR, FcεR, FcRn, C1q, and C3, mannan-binding lectin, mannose receptor, Staphylococcus Protein A, Staphylococcus Protein G, and viral FcγRs. The Fc ligands also include Fc receptor homologs (FcRH) (Davis et al., (2002) Immunological Reviews 190, 123-136), which are a family of Fc receptors homologous to FcγR. The Fc ligands also include unidentified molecules that bind to Fc.

FcγRI (CD64) including FcγRIa, FcγRIb, and FcγRIc, and FcγRIII (CD16) including isoforms FcγRIIIa (including allotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIIb-NA1 and FcγRIIIb-NA2) is composed of two types of subunits, α chain that binds to the Fc region of IgG and common γ chain having ITAM responsible for transduction of intracellular activation signal. Meanwhile, the cytoplasmic domain of FcγRII (CD32) including isoforms FcγRIIa (including allotypes H131 and R131) and FcγRIIc contains ITAM. These receptors are expressed on many immune cells such as macrophages, mast cells, and antigen-presenting cells. The activation signal transduced upon binding of these receptors to the Fc region of IgG results in enhancement of the phagocytic activity and inflammatory cytokine production of macrophages, mast cell degranulation, and the activation of antigen-presenting cells. Fcγ receptors having the ability to transduce the activation signal as described above are referred to as activating Fcγ receptors.

Meanwhile, the intracytoplasmic domain of FcγRIIb (including FcγRIIb-1 and FcγRIIb-2) contains ITIM responsible for transduction of inhibitory signals. The crosslinking between FcγRIIb and B cell receptor (BCR) on B cells suppresses the activation signal from BCR, which results in suppression of antibody production of B cells. The crosslinking of FcγRIII and FcγRIIb on macrophages suppresses the phagocytic activity and inflammatory cytokine production. Fcγ receptors having the ability to transduce the inhibitory signal as described above are referred to as inhibitory Fcγ receptors.

Receptor-binding domains that bind under a neutral pH range condition to Fcγ receptors more strongly than native human IgG can be produced by altering the amino acids of the Fc region of a human IgG. Such alterations include, for example, substitution, insertion, and deletion of one or more amino acids. Alternatively, an antigen-binding domain that binds to Fcγ receptor may be used as a receptor-binding domain. Such receptor-binding domains include Fab fragments that bind to FcγRIIIa, camel-derived single-domain antibodies, and the single-chain Fvs, described in Protein Eng Des Sel. 2009 March; 22(3): 175-88; Protein Eng Des Sel. 2008 January; 21(1): 1-10; and J Immunol. 2002 July 1; 169(1): 137-44; and FcγRI-binding cyclic peptides described in FASEB J. 2009 February; 23(2): 575-85. Whether the Fcγ receptor-binding activity of a receptor-binding domain is greater than that of the Fc region of native human IgG can be appropriately assessed using the methods described above.

In the present invention, the activity of binding to a human Fcγ receptor under an acidic pH range condition means human Fcγ receptor-binding activity at pH 4.0 to pH 6.5, preferably human Fcγ receptor-binding activity at pH 5.0 to pH 6.5, more preferably human Fcγ receptor-binding activity at any of pH 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, and 6.5, and particularly preferably human Fcγ receptor-binding activity at pH 5.8 to pH 6.0, which are close to the pH in the early endosome in vivo. Meanwhile, in the present invention, the binding activity to a human Fcγ receptor under a neutral pH range condition means human Fcγ receptor-binding activity at pH 6.7 to pH 10.0, preferably human Fcγ receptor-binding activity at pH 7.0 to pH 9.0, more preferably human Fcγ receptor-binding activity at any of pH 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0, and particularly preferably human Fcγ receptor-binding activity at pH 7.4, which is close to the pH of plasma in vivo.

Regarding measurement temperature, the binding affinity between a receptor-binding domain and a human Fcγ receptor may be measured at any temperature between 10° C. and 50° C. The binding affinity between a receptor-binding domain and a human Fcγ receptor is preferably determined at 15° C. to 40° C., more preferably at any of 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, and 35° C. Without being particularly limited, the 25° C. temperature is a preferred embodiment.

Receptor-binding domains of the present invention preferably include, for example, the Fc regions of human IgGs. The origin of such an Fc region is not particularly limited, and the domain can be obtained from any nonhuman animals or from humans. Nonhuman animals preferably include mice, rats, guinea pigs, hamsters, gerbils, cats, rabbits, dogs, goats, sheep, bovines, horses, camels, and nonhuman primates. In another embodiment, the receptor-binding domains can be obtained from cynomolgus monkeys, marmosets, rhesus monkeys, chimpanzees, and humans. The Fc regions are preferably obtained from the Fc region of human IgG1, and are not limited to particular IgG classes. Specifically, the Fc region of human IgG1, IgG2, IgG3, or IgG4 can be suitably used as a receptor-binding domain. Naturally occurring or artificially modified IgG variants include, for example, those described in published documents (Curr. Opin. Biotechnol. (2009) 20 (6), 685-91; Curr. Opin. Immunol. (2008) 20 (4), 460-470; Protein Eng. Des. Sel. (2010) 23 (4), 195-202; WO2009/086320; WO2008/092117; WO2007/041635; and WO2006/105338) but are not limited thereto.

As long as the receptor-binding domain binds under a neutral pH range condition to Fcγ receptor more strongly than native human IgG, amino acids may be altered at any positions. When receptor-binding domains are produced by altering the Fc region of human IgG1, amino acid alterations for increasing the binding activity to an Fcγ receptor under a neutral pH range condition includes, for example, the amino acid alterations described in WO2007/024249, WO2007/021841. WO2006/031370, WO2000/042072, WO2004/029207, WO2004/099249, WO2006/105338. WO2007/041635, WO2008/092117, WO2005/070963, WO2006/020114, WO2006/116260, and WO2006/023403.

Preferred amino acids when modifying the Fc region of IgG for receptor-binding domains that bind to human Fcγ receptor are, for example, at least one or more amino acids selected from the group consisting of the amino acids at positions 221, 222, 223, 224, 225, 227, 228, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 243, 244, 245, 246, 247, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 278, 279, 280, 281, 282, 283, 284, 285, 286, 288, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 307, 308, 309, 311, 312, 313, 314, 315, 316, 317, 318, 320, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 339, 341, 343, 375, 376, 377, 378, 379, 380, 382, 385, 386, 387, 389, 392, 396, 421, 423, 427, 428, 429, 430, 431, 433, 434, 436, 438, 440, and 442 according to EU numbering. Alteration of these amino acids increases the activity of an IgG Fc region to bind an Fcγ receptor under a neutral pH range condition.

Particularly preferred alterations for increasing the binding to an Fcγ receptor under a neutral pH range condition include, for example, alteration of at least one or more amino acids selected from the group consisting of:

the amino acid at position 221 which is Lys or Tyr; the amino acid at position 222 which is Phe, Trp, Glu, or Tyr; the amino acid at position 223 which is Phe, Trp, Glu, or Lys; the amino acid at position 224 which is Phe, Trp, Glu, or Tyr; the amino acid at position 225 which is Glu, Lys, or Trp; the amino acid at position 227 which is Glu, Gly, Lys, or Tyr; the amino acid at position 228 which is Glu, Gly, Lys, or Tyr; the amino acid at position 230 which is Ala, Glu, Gly, or Tyr; the amino acid at position 231 which is Glu, Gly, Lys, Pro, or Tyr; the amino acid at position 232 which is Glu, Gly, Lys, or Tyr; the amino acid at position 233 which is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 234 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 235 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 236 which is Ala, Asp, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 237 which is Ala, Asp, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 238 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 239 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 240 which is Ala, Ile, Met, or Thr; the amino acid at position 241 which is Asp, Glu, Leu, Arg, Trp, or Tyr; the amino acid at position 243 which is Leu, Glu, Leu, Gln, Arg, Trp, or Tyr; the amino acid at position 244 which is His; the amino acid at position 245 which is Ala; the amino acid at position 246 which is Asp, Glu, His, or Tyr; the amino acid at position 247 which is Ala, Phe, Gly, His, Ile, Leu, Met, Thr, Val, or Tyr; the amino acid at position 249 which is Glu, His, Gln, or Tyr; the amino acid at position 250 which is Glu or Gln; the amino acid at position 251 which is Phe; the amino acid at position 254 which is Phe, Met, or Tyr; the amino acid at position 255 which is Glu, Leu, or Tyr; the amino acid at position 256 which is Ala, Met, or Pro; the amino acid at position 258 which is Asp, Glu, His, Ser, or Tyr; the amino acid at position 260 which is Asp, Glu, His, or Tyr; the amino acid at position 262 which is Ala, Glu, Phe, Ile, or Thr; the amino acid at position 263 which is Ala, Ile, Met, or Thr; the amino acid at position 264 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 265 which is Ala, Glu, Leu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 266 which is Ala, Phe, Ile, Leu, Met, or Thr; the amino acid at position 267 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 268 which is Ala, Asp, Glu, Phe, Gly, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, or Trp: the amino acid at position 269 which is Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 270 which is Glu, Phe, Gly, His, Ile, Leu, Met, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 271 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 272 which is Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 273 which is Phe or Ile; the amino acid at position 274 which is Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 275 which is Leu or Trp; the amino acid at position 276 which is Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 278 which is Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp; the amino acid at position 279 which is Ala; the amino acid at position 280 which is Ala, Gly, His, Lys, Leu, Pro, Gln, Trp, or Tyr; the amino acid at position 281 which is Asp, Lys, Pro, or Tyr; the amino acid at position 282 which is Glu, Gly, Lys, Pro, or Tyr; the amino acid at position 283 which is Ala, Gly, His, Ile, Lys, Leu, Met, Pro, Arg, or Tyr; the amino acid at position 284 which is Asp, Glu, Leu, Asn, Thr, or Tyr; the amino acid at position 285 which is Asp, Glu, Lys, Gln, Trp, or Tyr; the amino acid at position 286 which is Glu, Gly, Pro, or Tyr; the amino acid at position 288 which is Asn, Asp, Glu, or Tyr; the amino acid at position 290 which is Asp, Gly, His, Leu, Asn, Ser, Thr, Trp, or Tyr; the amino acid at position 291 which is Asp, Glu, Gly, His, Ile, Gln, or Thr; the amino acid at position 292 which is Ala, Asp, Glu, Pro, Thr, or Tyr; the amino acid at position 293 which is Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 294 which is Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 295 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 296 which is Ala, Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, or Val; the amino acid at position 297 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 298 which is Ala, Asp, Glu, Phe, His, Ile, Lys, Met, Asn, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 299 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 300 which is Ala, Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp: the amino acid at position 301 which is Asp, Glu, His, or Tyr; the amino acid at position 302 which is Ile: the amino acid at position 303 which is Asp, Gly, or Tyr; the amino acid at position 304 which is Asp, His, Leu, Asn, or Thr; the amino acid at position 305 which is Glu, Ile, Thr, or Tyr; the amino acid at position 311 which is Ala, Asp, Asn, Thr, Val, or Tyr; the amino acid at position 313 which is Phe; the amino acid at position 315 which is Leu; the amino acid at position 317 which is Glu or Gln; the amino acid at position 318 which is His, Leu, Asn, Pro, Gln, Arg, Thr, Val, or Tyr, the amino acid at position 320 which is Asp, Phe, Gly, His, Ile, Leu, Asn, Pro, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 322 which is Ala, Asp, Phe, Gly, His, Ile, Pro, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 323 which is Ile, Leu, or Met; the amino acid at position 324 which is Asp, Phe, Gly, His, Ile, Leu, Met, Pro, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 325 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 326 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 327 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 328 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 329 which is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 330 which is Cys, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 331 which is Asp, Phe, His, Ile, Leu, Met, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 332 which is Ala, Asp, Glu, Phe, Gly, His, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 333 which is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 334 which is Ala, Glu, Phe, His, Ile, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 335 which is Asp, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 336 which is Glu, Lys, or Tyr; the amino acid at position 337 which is Asp, Glu, His, or Asn; the amino acid at position 339 which is Asp, Phe, Gly, Ile, Lys, Met, Asn, Gln, Arg, Ser, or Thr; the amino acid at position 376 which is Ala or Val; the amino acid at position 377 which is Gly or Lys; the amino acid at position 378 which is Asp; the amino acid at position 379 which is Asn; the amino acid at position 380 which is Ala, Asn, or Ser; the amino acid at position 382 which is Ala or Ile; the amino acid at position 385 which is Glu; the amino acid at position 392 which is Thr; the amino acid at position 396 which is Asp, Glu, Phe, Ile, Lys, Leu, Met, Gln, Arg, or Tyr; the amino acid at position 421 which is Lys; the amino acid at position 427 which is Asn; the amino acid at position 428 which is Phe or Leu; the amino acid at position 429 which is Met; the amino acid at position 434 which is Trp; the amino acid at position 436 which is Ile; and the amino acid at position 440 is Gly, His, Ile, Leu, or Tyr, according to EU numbering in the Fc region. Further, the number of amino acids to be altered is not particularly limited, and amino acids may be modified at only one site, or two or more sites. Combinations of amino acid alterations at two or more sites include, for example, those described in Tables 5-1 to 5-3.

TABLE 5-1 AMINO ACID COMBINATION AMINO ACID COMBINATION K370E/P396L/D270E S239Q/I332Q Q419H/P396L/D270E S267D/I332E V240A/P396L/D270E S267E/I332E R255L/P396L/D270E S267L/A327S R255L/P396L/D270E S267Q/A327S R255L/P396L/D270E/R292G S298A/I332E R255L/P396L/D270E S304T/I332E R255L/P396L/D270E/Y300L S324G/I332D F243L/D270E/K392N/P396L S324G/I332E F243L/R255L/D270E/P396L S324I/I332D F243L/R292P/Y300L/V305I/P396L S324I/I332E F243L/R292P/Y300L/P396L T260H/I332E F243L/R292P/Y300L T335D/I332E F243L/R292P/P396L V240I/V266I F243L/R292P/V305I V264I/I332E F243L/R292P D265F/N297E/I332E S298A/E333A/K334A D265Y/N297D/I332E E380A/T307A F243L/V262I/V264W K326M/E333S N297D/A330Y/I332E K326A/E333A N297D/T299E/I332E S317A/K353A N297D/T299F/I332E A327D/I332E N297D/T299H/I332E A330L/I332E N297D/T299I/I332E A330Y/I332E N297D/T299L/I332E E258H/I332E N297D/T299V/I332E E272H/I332E P230A/E233D/I332E E272I/N276D P244H/P245A/P247V E272R/I332E S239D/A330L/I332E E283H/I332E S239D/A330Y/I332E E293R/I332E S239D/H268E/A330Y F241L/V262I S239D/I332E/A327A F241W/F243W S239D/I332E/A330I

Table 5-2 is a continuation of Table 5-1.

TABLE 5-2 F243L/V264I S239D/N297D/I332E H268D/A330Y S239D/S298A/I332E H268E/A330Y S239D/V264I/I332E K246H/I332E S239E/N297D/I332E L234D/I332E S239E/V264I/I332E L234E/I332E S239N/A330L/I332E L234G/I332E S239N/A330Y/I332E L234I/I332E S239N/S298A/I332E L234I/L235D S239Q/V264I/I332E L234Y/I332E V264E/N297D/I332E L235D/I332E V264I/A330L/I332E L235E/I332E V264I/A330Y/I332E L235I/I332E V264I/S298A/I332E L235S/I332E Y296D/N297D/I332E L328A/I332D Y296E/N297D/I332E L328D/I332D Y296H/N297D/I332E L328D/I332E Y296N/N297D/I332E L328E/I332D Y296Q/N297D/I332E L328E/I332E Y296T/N297D/I332E L328F/I332D D265Y/N297D/T299L/I332E L328F/I332E F241E/F243Q/V262T/V264E L328H/I332E F241E/F243R/V262E/V264R L328I/I332D F241E/F243Y/V262T/V264R L328I/I332E F241L/F243L/V262I/V264I L328M/I332D F241R/F243Q/V262T/V264R L328M/I332E F241S/F243H/V262T/V264T L328N/I332D F241W/F243W/V262A/V264A L328N/I332E F241Y/F243Y/V262T/V264T L328Q/I332D I332E/A330Y/H268E/A327A L328Q/I332E N297D/I332E/S239D/A330L L328T/I332D N297D/S298A/A330Y/I332E L328T/I332E S239D/A330Y/I332E/K326E L328V/I332D S239D/A330Y/I332E/K326T L328V/I332E S239D/A330Y/I332E/L234I L328Y/I332D S239D/A330Y/I332E/L235D

Table 5-3 is a continuation of Table 5-2.

TABLE 5-3 L328Y/I332E S239D/A330Y/I332E/V240I N297D/I332E S239D/A330Y/I332E/V264T N297E/I332E S239D/A330Y/I332E/V266I N297S/I332E S239D/D265F/N297D/I332E P227G/I332E S239D/D265H/N297D/I332E P230A/E233D S239D/D265I/N297D/I332E Q295E/I332E S239D/D265L/N297D/I332E R255Y/I332E S239D/D265T/N297D/I332E S239D/I332D S239D/D265V/N297D/I332E S239D/I332E S239D/D265Y/N297D/I332E S239D/I332N S239D/I332E/A330Y/A327A S239D/I332Q S239D/I332E/H268E/A327A S239E/D265G S239D/I332E/H268E/A330Y S239E/D265N S239D/N297D/I332E/A330Y S239E/D265Q S239D/N297D/I332E/K326E S239E/I332D S239D/N297D/I332E/L235D S239E/I332E S239D/V264I/A330L/I332E S239E/I332N S239D/V264I/S298A/I332E S239E/I332Q S239E/V264I/A330Y/I332E S239N/I332D F241E/F243Q/V262T/V264E/I332E S239N/I332E F241E/F243R/V262E/V264R/I332E S239N/I332N F241E/F243Y/V262T/V264R/I332E S239N/I332Q F241R/F243Q/V262T/V264R/I332E S239Q/I332D S239D/I332E/H268E/A330Y/A327A S239Q/I332E S239E/V264I/S298A/A330Y/I332E S239Q/I332N F241Y/F243Y/V262T/V264T/N297D/I332E S267E/L328F G236D/S267E S239D/S267E

Herein, the activity to bind a human Fcγ receptor is deemed to be greater than that of native human IgG when the activity to bind human Fey receptors FcγRI, FcγRIIa, FcγRIIb, FcγRIIIa, and/or FcγRIIIb, is greater than that of native human IgG. This means that, for example, the activity to bind a human Fcγ receptor is 105% or more, preferably 110% or more, 115% or more, 120% or more, 125% or more, particularly preferably 130% or more, 135% or more, 140% or more, 145% or more, 150% or more, 155% or more, 160% or more, 165% or more, 170% or more, 175% or more, 180% or more, 185% or more, 190% or more, 195% or more, twice or more, 2.5 times or more, 3 times or more, 3.5 times or more, 4 times or more, 4.5 times or more, 5 times or more, 7.5 times or more, 10 times or more, 20 times or more, 30 times or more, 40 times or more, 50 times or more, 60 times or more, 70 times or more, 80 times or more, 90 times or more, or 100 times or more than that of native human IgG.

Receptor-binding domains of the present invention may have the property of having a greater binding activity to a specific Fcγ receptor(s) than the binding activity to other Fcγ receptors (selectively binds to a specific Fcγ receptor(s)). Examples include a receptor-binding domain having a greater binding activity to an inhibitory Fcγ receptor than to an activating Fcγ receptor. Such receptor-binding domains preferably include those having a greater binding activity to FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), which is an inhibitory Fcγ receptor, than to an activating Fcγ receptor selected from:

FcγRI (CD64) including isoforms FcγRIa, FcγRIb, and FcγRIc; FcγRIII (CD16) including isoforms FcγRIIIa (including allotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIIb-NA1 and FcγRIIIb-NA2); and FcγRII (CD32) including isoforms FcγRIIa (including allotypes H131 and R131) and FcγRIIc. The receptor-binding domains particularly preferably include those having a greater binding activity to FcγRIIb-1 and/or FcγRIIb-2 than to FcγRIIa (allotype H131).

Whether a receptor-binding domain has the property of selectively binding to a specific Fcγ receptor can be determined by measuring and comparing the KD value of the receptor-binding domain for each Fcγ receptor. For example, when the KD value of a receptor-binding domain to an activating Fcγ receptor divided by its KD value to an inhibitory Fcγ receptor is 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2 or more, 3 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 60 or more, 65 or more, 70 or more, 75 or more, 80 or more, 85 or more, 90 or more, 95 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, 160 or more, 170 or more, 180 or more, 190 or more, 200 or more, 210 or more, 220 or more, 230 or more, 240 or more, 250 or more, 260 or more, 270 or more, 280 or more, 290 or more, 300 or more, 310 or more, 320 or more, 330 or more, 340 or more, 350 or more, 360 or more, 370 or more, 380 or more, 390 or more, 400 or more, 410 or more, 420 or more, 430 or more, 440 or more, 450 or more, 460 or more, 470 or more, 480 or more, 490 or more, 500 or more, 520 or more, 540 or more, 560 or more, 580 or more, 600 or more, 620 or more, 640 or more, 660 or more, 680 or more, 700 or more, 720 or more, 740 or more, 760 or more, 780 or more, 800 or more, 820 or more, 840 or more, 860 or more, 880 or more, 900 or more, 920 or more, 940 or more, 960 or more, 980 or more, 1000 or more, 1500 or more, 2000 or more, 2500 or more, 3000 or more, 3500 or more, 4000 or more, 4500 or more, 5000 or more, 5500 or more, 6000 or more, 6500 or more, 7000 or more, 7500 or more, 8000 or more, 8500 or more, 9000 or more, 9500 or more, 10000 or more, or 100000 or more, it is determined that the receptor-binding domain may bind more selectively to the inhibitory Fcγ receptor than to the activating Fcγ receptor.

Without being particularly limited thereto, receptor-binding domains having a greater binding activity to an inhibitory Fcγ receptor than to an activating Fcγ receptor (selectively binds to an inhibitory Fcγ receptor) preferably include, for example, the IgG Fc region variants described in WO2012/115241, such as Fc regions with alterations of the amino acids at positions 238 and/or 328 (EU numbering) into different amino acids in IgG Fc region, more preferably Fc regions with alteration of the amino acid at position 238 into Asp and/or alteration of the amino acid at position 328 into Glu. Furthermore, it is possible to select appropriate IgG Fc region variants described in US2009/0136485.

At least one different alteration may be added to IgG Fc regions in combination with the above-described alterations. It is preferable that as a result of the alteration, the binding activity to FcγRIIb is increased, and the binding activity to FcγRIIa (allotype H131) and FcγRIIa (allotype R131) is maintained or is reduced. Such alteration improves the binding selectivity for FcγRIIb over FcγRIIa. Alteration that improves the binding selectivity for FcγRIIb over FcγRIIa (allotype R131) is preferred, and alteration that improves the binding selectivity for FcγRIIb over FcγRIIa (allotype R131) and FcγRIIa (allotype H131) is more preferred. Without being particularly limited thereto, such alterations include, for example, at least one or more amino acid alterations selected from the following group:

the amino acid at position 233 is Asp; the amino acid at position 234 is Trp or Tyr; the amino acid at position 235 is Phe, Trp, or Tyr; the amino acid at position 236 is Asp, the amino acid at position 237 is Ala, Asp, Glu, Phe, Leu, Met, Trp, or Tyr; the amino acid at position 238 is Phe or Leu; the amino acid at position 239 is Asp, Glu, Gly, Leu, or Asn; the amino acid at position 266 is Ile, Leu, or Met; the amino acid at position 267 is Ala, Asp, Glu, Ile, Met, Gln, or Val; the amino acid at position 268 is Ala, Asp, Glu, Gly, Asn, or Gln; the amino acid at position 271 is Gly or Leu; the amino acid at position 295 is Leu; the amino acid at position 296 is Asp; the amino acid at position 300 is Asp, Glu, or Gln; the amino acid at position 323 is Ile, Leu, or Met; the amino acid at position 324 is Ile or Val; the amino acid at position 325 is Met or Ser; the amino acid at position 326 is Ala, Asp, Glu, Phe, His, Ile, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 327 is Asp, Glu, Gly, or Asn; the amino acid at position 328 is Ala, Asp, Phe, Ile, Met, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 330 is Lys, Met, or Arg; the amino acid at position 331 is Phe, Trp, or Tyr; the amino acid at position 332 is Phe; the amino acid at position 333 is Pro; the amino acid at position 334 is Ala, Trp, Glu, Phe, His, Ile, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 335 is Asp; and the amino acid at position 337 is Asp according to EU numbering.

Among the above, preferred alterations include, for example, at least one or more amino acid alterations selected from the following group:

the amino acid at position 233 is Asp; the amino acid at position 234 is Trp or Tyr; the amino acid at position 237 is Ala, Asp, Glu, Phe, Leu, Met, Trp, or Tyr; the amino acid at position 239 is Asp; the amino acid at position 267 is Ala, Gln, or Val; the amino acid at position 268 is Asp, Glu, or Asn; the amino acid at position 271 is Gly; the amino acid at position 296 is Asp; the amino acid at position 323 is Ile, Leu, or Met; the amino acid at position 326 is Ala, Asp, Glu, Leu, Met, Asn, Gln, Ser, or Thr; and the amino acid at position 330 is Lys, Met, or Arg according to EU numbering.

The alterations described above may be an alteration at one site, or at two or more sites in combination. Preferred alterations include, for example, the alterations shown in Tables 24 to 25, 27 to 34, and 36 to 37.

Without being particularly limited thereto, one embodiment of the receptor-binding domain included in antigen-binding molecules of the present invention includes altered Fc regions of human IgG1 (SEQ ID NO: 49), IgG2 (SEQ ID NO: 50), IgG3 (SEQ ID NO: 51), and IgG4 (SEQ ID NO: 52). Examples of the altered Fc regions include the Fc regions of human IgGs (IgG1, IgG2, IgG3, and IgG4), in which the amino acid at position 238 (EU numbering) is Asp and the amino acid at position 271 (EU numbering) is Gly. The Fc regions of human IgGs (IgG1, IgG2, IgG3, and IgG4) in which the amino acid at position 238 (EU numbering) is Asp and the amino acid at position 271 is Gly, and antigen-binding molecules containing the Fc regions exhibit a greater binding activity to the inhibitory Fcγ receptor rather than to the activating Fcγ receptor.

In the present invention, at least one different alteration may be added to the Fc region in which the amino acid at position 238 (EU numbering) is Asp and the amino acid at position 271 is Gly (EU numbering). It is preferable that as a result, the binding activity to FcγRIIb-1 and/or FcγRIIb-2 is increased, and the binding activity to FcγRIIa (allotype H131) and FcγRIIa (allotype R131) is maintained or is reduced. It is also preferable that the level of increase in the binding activity to the inhibitory Fcγ receptor (FcγRIIb-1 and/or FcγRIIb-2) is higher than the level of increase in the binding activity to the activating Fcγ receptor (FcγRIa, FcγRIb, FcγRIc, FcγRIIIa (allotype V158), FcγRIIIa (allotype F158), FcγRIIIb (allotype FcγRIIIb-NA1), FcγRIIIb (allotype FcγRIIIb-NA2). FcγRIIa (allotype H131), and FcγRIIa (allotype R131)). Such alteration improves the binding selectivity for FcγRIIb over FcγRIIa.

Without being particularly limited thereto, selective receptor-binding domains include, for example. Fc regions of a human IgG (IgG1, IgG2, IgG3, or IgG4) in which the amino acid at position 238 (EU numbering) is altered to Asp and the amino acid at position 271 is altered to Gly, and in which one or more of the amino acids at positions 233, 234, 237, 244, 245, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262, 264, 265, 266, 267, 268, 269, 270, 272, 279, 283, 285, 286, 288, 293, 296, 307, 308, 309, 311, 312, 314, 316, 317, 318, 326, 327, 330, 331, 332, 333, 339, 341, 343, 375, 376, 377, 378, 380, 382, 385, 386, 387, 389, 396, 423, 427, 428, 430, 431, 433, 434, 436, 438, 440, and 442 according to EU numbering are altered.

Furthermore, without being particularly limited thereto, selective receptor-binding domains include, for example, Fc regions of a human IgG (IgG1, IgG2, IgG3, or IgG4) in which

the amino acid at position 238 (EU numbering) is altered to Asp and the amino acid at position 271 is altered to Gly, and in which one or more amino acid alterations selected from the following group are made: the amino acid at position 233 is Asp; the amino acid at position 234 is Tyr; the amino acid at position 237 is Asp; the amino acid at position 264 is Ile; the amino acid at position 265 is Glu; the amino acid at position 266 is Phe, Met, or Leu; the amino acid at position 267 is Ala, Glu, Gly, or Gln; the amino acid at position 268 is Asp or Glu; the amino acid at position 269 is Asp; the amino acid at position 272 is Asp. Phe, Ile, Met, Asn, or Gln; the amino acid at position 296 is Asp; the amino acid at position 326 is Ala or Asp; the amino acid at position 327 is Gly; the amino acid at position 330 is Lys or Arg; the amino acid at position 331 is Ser; the amino acid at position 332 is Thr; the amino acid at position 333 is Thr, Lys, or Arg; and the amino acid at position 396 is Asp, Glu, Phe, Ile, Lys, Leu, Met. Gln, Arg, or Tyr, according to EU numbering.

Without being particularly limited thereto, one embodiment of the above-described Fc regions includes, for example, those described in Tables 6-1 to 6-6.

TABLE 6-1 ALTERED Fc REGION ALTERED AMINO ACID (EU NUMBERING) BP208 E233D/G237D/P238D/H268D/P271G/A330R BP209 G237D/P238D/H268D/P271G/K326A/A330R BP210 G237D/P238D/H268D/P271G/A330R BP211 E233D/P238D/H268D/P271G/K326A/A330R BP212 E233D/P238D/H268D/P271G/Y296D/A330R BP213 E233D/P238D/H268D/P271G/A330R BP214 E233D/L234Y/G237D/P238D/Y296D/K326D/A330K BP215 G237D/P238D/H268D/P271G/Y296D/A330K BP216 G237D/P238D/S267Q/H268D/P271G/A330K BP217 G237D/P238D/S267Q/H268D/P271G/Y296D/A330K BP218 G237D/P238D/H268D/P271G/K326D/A330K BP219 L234Y/G237D/P238D/H268D/P271G/A330K BP220 E233D/G237D/P238D/H268D/P271G/Y296D/A330K BP221 L234Y/G237D/P238D/Y296D/K326A/A330R BP222 L234Y/G237D/P238D/P271G/K326A/A330R BP223 L234Y/G237D/P238D/H268D/P271G/K326A/A330R BP224 L234Y/G237D/P238D/S267Q/H268D/P271G/K326A/ A330R BP225 L234Y/G237D/P238D/K326D/A330R BP226 L234Y/G237D/P238D/P271G/K326D/A330R BP227 L234Y/G237D/P238D/H268D/P271G/K326D/A390R BP228 L234Y/G237D/P238D/S267Q/H268D/P271G/K326D/ A330R BP229 E233D/L234Y/G237D/P238D/P271G/K326A/A330R BP230 E233D/G237D/P238D/H268D/P271G/Y296D/A330R BP231 G237D/P238D/H268D/P271G/Y296D/A330R BP232 L234Y/G237D/P238D/P271G/K326A/A330K BP233 L234Y/G237D/P238D/P271G/A330K BP234 E233D/L234Y/G237D/P238D/S267Q/H268D/P271G/ Y296D/K326D/A330K BP235 E233D/L234Y/G237D/P238D/H268D/P271G/Y296D/ K326D/A330R BP236 E233D/L234Y/G237D/P238D/S267Q/H268D/P271G/ Y296D/K326D/A330R BP237 E233D/L234Y/G237D/P238D/S267Q/H268D/P271G/ Y296D/K326A/A330K

Table 6-2 is a continuation table of Table 6-1.

TABLE 6-2 ALTERED Fc REGION ALTERED AMINO ACID (EU NUMBERING) BP238 E233D/L234Y/G237D/P238D/H268D/P271G/Y296D/K326A/A330R BP239 E233D/L234Y/G237D/P238D/S267Q/H268D/P271G/Y296D/K326A/A330R BP240 E233D/G237D/P238D/S267Q/H268D/P271G/A330R BP241 E233D/G237D/P238D/H268D/P271G/K326D/A330R BP242 E233D/G237D/P238D/H268D/P271G/K326A/A330R BP243 E233D/L234Y/G237D/P238D/H268D/P271G/A330R BP244 E233D/G237D/P238D/S267Q/E268D/P271G/Y296D/A330R BP245 E233D/G237D/P238D/S267Q/H268D/P271G/Y296D/K326D/A330R BP246 E233D/G237D/P238D/S267Q/H268D/P271G/Y296D/K326A/A330R BP247 E233D/G237D/P238D/H268D/P271G/Y296D/K326D/A330R BP248 E233D/G237D/P238D/H268D/P271G/Y296D/K326A/A330R BP249 E233D/L234Y/G237D/P238D/H268D/P271G/Y296D/A330R BP262 G237D/P238D/H268E/P271G BP264 E233D/G237D/P238D/H268E/P271G/Y296D/A330R BP265 G237D/P238D/H268E/P271G/Y296D/A330R BP266 E233D/G237D/P238D/H268E/P271G/A330R BP267 E233D/G237D/P238D/H268E/P271G BP268 E233D/G237D/P238D/H268E/P271G/Y296D BP269 G237D/P238D/H268E/P271G/Y296D BP300 E233D/G237D/P238D/V264I/H268E/P271G BP313 E233D/G237D/P238D/D265E/H268E/P271G BP333 E233D/G237D/P238D/V266F/H268E/P271G BP338 E233D/G237D/P238D/V266L/H268E/P271G BP339 E233D/G237D/P238D/V266M/H268E/P271G BP348 E233D/G237D/P238D/S267A/H268E/P271G BP350 E233D/G237D/P238D/S267E/H268E/P271G BP352 E233D/G237D/P238D/S267G/H268E/P271G BP367 E233D/G237D/P238D/H268E/E269D/P271G BP384 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/K334R BP390 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/I332S BP391 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/I332T

Table 6-3 is a continuation table of Table 6-2.

TABLE 6-3 ALTERED Fc REGION ALTERED AMINO ACID (EU NUMBERING) BP392 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/I332K BP393 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/I332R BP423 E233D/G237D/P238D/S267A/H268E/P271G/A330R BP425 E233D/G237D/P238D/V266L/S267A/H268E/P271G/A330R BP426 E233D/G237D/P238D/S267A/H268E/E269D/P271G/A330R BP427 E233D/G237D/P238D/S267A/H268E/E269Y/P271G/A330R BP428 E233D/G237D/P238D/S267G/H268E/P271G/A330R BP429 E233D/G237D/P238D/V264I/S267G/H268E/P271G/A330R BP430 E233D/G237D/P238D/V266L/S267G/H268E/P271G/A330R BP431 E233D/G237D/P238D/S267G/H268E/E269D/P271G/A330R BP432 E233D/G237D/P238D/S267G/H268E/E269Y/P271G/A330R BP433 E233D/G237D/P238D/H268D/P271G/Y296D/A330K/I332T BP434 E233D/G237D/P238D/H268D/P271G/Y296D/K326D/A330R/I332T BP435 E233D/G237D/P238D/H268D/P271G/Y296D/K326A/A330R/I332T BP436 E233D/G237D/P238D/S267A/H268E/P271G/Y296D/A330R/I332T BP437 G237D/P238D/S267A/H268E/P271G/Y296D/A330R/I332T BP438 E233D/G237D/P238D/S267A/H268E/P271G/A330R/I332T BP439 E233D/G237D/P238D/V264I/V266L/S267A/H268E/P271G/A330R BP440 E233D/G237D/P238D/V264I/H268E/P271G/A330R BP441 E233D/G237D/P238D/V266L/H268E/P271G/A330R BP442 E233D/G237D/P238D/H268E/E269D/P271G/A330R BP443 E233D/G237D/P238D/V266L/H268E/E269D/P271G/A330R BP444 E233D/G237D/P238D/H268E/E269N/P271G/A330R BP445 E233D/G237D/P238D/V264I/S267A/H268E/P271G/A330R BP446 E233D/G237D/P238D/S267A/H268E/E269N/P271G/A330R BP447 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396A BP448 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396D BP449 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396E BP450 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396F BP451 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396G BP452 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396H

Table 6-4 is a continuation table of Table 6-3.

TABLE 6-4 ALTERED Fc REGION ALTERED AMINO ACID (EU NUMBERING) BP453 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396I BP454 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396K BP455 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396L BP456 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396M BP457 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396N BP458 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396Q BP459 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396R BP460 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396S BP461 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396T BP462 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396V BP463 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396W BP464 E233D/G237D/P238D/S267A/H268E/P271G/A330R/P396Y BP465 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E333K BP466 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E333R BP467 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E334S BP468 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E334T BP469 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E333S BP470 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/E333T BP471 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/P331S BP472 E233D/G237D/P238D/H268D/P271G/Y296D/A330S BP473 E233D/G237D/P238D/H268D/P271G/Y296D/A327G/A330R BP474 E233D/G237D/P238D/H268D/P271G/Y296D/A330R/P331S BP475 E233D/G237D/P238D/H268D/P271G/Y296D/A327G/A330S BP476 E233D/G237D/P238D/H268D/P271G/Y296D/A327G/A330S/P331S BP477 E233D/G237D/P238D/H268D/P271G/Y296D/A327G/A330R/P331S BP478 E233D/G237D/P238D/H268D/P271G/Y296D/A330R + S131C/K133R/G137E/G138S/Q196K/I199T/N203D/K214R/P217S + 219-221 DELETION + K222Y/T223G/H224P/T225P BP479 E233D/G237D/P238D/V264I/V266L/S267A/H268E/P271G BP480 E233D/G237D/P238D/V266L/H268E/E269D/P271G BP481 E233D/G237D/P238D/V264I/S267A/H268E/P271G

Table 6-5 is a continuation table of Table 6-4.

TABLE 6-5 ALTERED Fc REGION ALTERED AMINO ACIDS (EU NUMBERING) BP482 E233D/G237D/P238D/S267A/H268E/E269N/P271G BP483 E233D/G237D/P238D/V266L/S267A/H268E/P271G BP484 E233D/G237D/P238D/S267A/H268E/E269D/P271G BP485 E233D/G237D/P238D/S267A/H268E/E269Y/P271G BP487 E233D/G237D/P238D/V264I/S267A/H268E/P271G/A330R/P396M BP488 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A330R BP489 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A330R/P396M BP490 G237D/P238D/V264I/S267A/H268E/P271G/A330R BP491 G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A330R BP492 P238D/V264I/S267A/H268E/P271G BP493 P238D/V264I/S267A/H268E/P271G/Y296D BP494 G237D/P238D/S267A/H268E/P271G/Y296D/A330R BP495 G237D/P238D/S267G/H268E/P271G/Y296D/A330R BP496 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D BP497 E233D/G237D/P238D/V264I/S267A/H268E/P271G/A327G/A330R BP498 E233D/G237D/P238D/V264I/S267A/H268E/P271G/A330R/P396L BP499 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A330R/P396L BP500 G237D/P238D/V264I/S267A/H268E/P271G/Y296D BP501 G237D/P238D/V264I/S267A/H268E/P271G BP502 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A327G/A330R BP503 E233D/G237D/P238D/V264I/S267A/H268E/P271G/Y296D/A327G/A330R/P396M BP504 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272P BP505 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272D BP506 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272P/Y296D/A330R BP507 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272P/A330R BP508 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272P/Y296D BP509 E233D/G237D/P238D/V264I/S267A/H268E/P271G/E272D/Y296D BP510 G237D/P238D/V264I/S267A/H268E/P271G/E272P/A330R BP511 G237D/P238D/V264I/S267A/H268E/P271G/E272P/Y296D/A330R BP513 E233D/G237D/P238D/H268E/E272D/P271G

Table 6-6 is a continuation table of Table 6-5.

TABLE 6-6 ALTERED Fc REGION ALTERED AMINO ACIDS (EU NUMBERING) BP514 E233D/G237D/P238D/H268E/E272F/P271G BP517 E233D/G237D/P238D/H268E/E272I/P271G BP520 E233D/G237D/P238D/H268E/E272M/P271G BP521 E233D/G237D/P238D/H268E/E272N/P271G BP523 E233D/G237D/P238D/H268E/E272Q/P271G

It is preferable that the above-described receptor-binding domains which bind to human Fcγ receptor further contain amino acid alterations that enhance the FcRn-binding under an acidic pH range condition. Amino acids that can be altered as such include, for example:

the amino acids at positions 252, 254, 256, 309, 311, 315, 433, and/or 434 (EU numbering), and in combination with these described above, the amino acids at positions 253, 310, 435, and/or 426 (EU numbering), as described in WO1997/034631; the amino acids at positions 238, 252, 253, 254, 255, 256, 265, 272, 286, 288, 303, 305, 307, 309, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 386, 388, 400, 413, 415, 424, 433, 434, 435, 436, 439, and/or 447 (EU numbering), as described in WO2000/042072; the amino acids at positions 251, 252, 254, 255, 256, 308, 309, 311, 312, 385, 386, 387, 389, 428, 433, 434, and/or 436 (EU numbering), as described in WO2002/060919; the amino acids at positions 250, 314, and 428 (EU numbering), as described in WO2004/092219; the amino acids at positions 238, 244, 245, 249, 252, 256, 257, 258, 260, 262, 270, 272, 279, 283, 285, 286, 288, 293, 307, 311, 312, 316, 317, 318, 332, 339, 341, 343, 375, 376, 377, 378, 380, 382, 423, 427, 430, 431, 434, 436, 438, 440, and/or 442 (EU numbering), as described in WO2006/020114; and the amino acids at positions 251, 252, 307, 308, 378, 428, 430, 434, and/or 436 (EU numbering), as described in WO2010/045193. Alterations of these amino acids enhance the FcRn-binding of IgG Fc regions under an acidic pH range condition.

More specifically, such alterations include, for example, at least one or more amino acid alterations selected from the following group:

the amino acid at position 244 is Leu; the amino acid at position 245 is Arg; the amino acid at position 249 is Pro; the amino acid at position 250 is Gln or Glu; the amino acid at position 251 is Arg, Asp, Glu, or Leu; the amino acid at position 252 is Phe, Ser, Thr, or Tyr; the amino acid at position 254 is Ser or Thr; the amino acid at position 255 is Arg, Gly, Ile, or Leu; the amino acid at position 256 is Ala, Arg, Asn, Asp, Gln, Glu, Pro, or Thr; the amino acid at position 257 is Ala, Ile, Met, Asn, Ser, or Val; the amino acid at position 258 is Asp; the amino acid at position 260 is Ser; the amino acid at position 262 is Leu; the amino acid at position 270 is Lys; the amino acid at position 272 is Leu or Arg; the amino acid at position 279 is Ala, Asp, Gly, His, Met, Asn, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 283 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 285 is Asn; the amino acid at position 286 is Phe; the amino acid at position 288 is Asn or Pro; the amino acid at position 293 is Val; the amino acid at position 307 is Ala, Glu, Gln, or Met; the amino acid at position 308 is lie, Pro, or Thr; the amino acid at position 309 is Pro; the amino acid at position 311 is Ala, Glu. Ile, Lys, Leu, Met, Ser, Val, or Trp; the amino acid at position 312 is Ala, Asp, or Pro; the amino acid at position 314 is Ala or Leu; the amino acid at position 316 is Lys; the amino acid at position 317 is Pro; the amino acid at position 318 is Asn or Thr; the amino acid at position 332 is Phe, His, Lys, Leu, Met, Arg, Ser, or Trp; the amino acid at position 339 is Asn, Thr, or Trp; the amino acid at position 341 is Pro, the amino acid at position 343 is Glu, His, Lys, Gln, Arg, Thr, or Tyr; the amino acid at position 375 is Arg; the amino acid at position 376 is Gly, Ile, Met, Pro, Thr, or Val; the amino acid at position 377 is Lys; the amino acid at position 378 is Asp. Asn, or Val; the amino acid at position 380 is Ala, Asn, Ser, or Thr; the amino acid at position 382 is Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 385 is Ala, Arg, Asp, Gly, His, Lys, Ser, or Thr; the amino acid at position 386 is Arg, Asp, Ile, Lys, Met, Pro, Ser, or Thr; the amino acid at position 387 is Ala, Arg, His, Pro, Ser, or Thr; the amino acid at position 389 is Asn, Pro, or Ser; the amino acid at position 423 is Asn; the amino acid at position 427 is Asn; the amino acid at position 428 is Leu, Met, Phe, Ser, or Thr; the amino acid at position 430 is Ala, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 431 is His or Asn; the amino acid at position 433 is Arg, Gln, His, Ile, Lys, Pro, or Ser; the amino acid at position 434 is Ala, Gly, His. Phe, Ser, Trp, or Tyr; the amino acid at position 436 is Arg, Asn, His, Ile, Leu, Lys, Met, or Thr; the amino acid at position 438 is Lys, Leu, Thr, or Trp; the amino acid at position 440 is Lys; and the amino acid at position 442 is Lys, according to EU numbering.

Alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 308 is Ile, the amino acid at position 309 is Pro, and/or the amino acid at position 311 is Glu; an alteration comprising the amino acid at position 308 is Thr, the amino acid at position 309 is Pro, the amino acid at position 311 is Leu, the amino acid at position 312 is Ala, and/or the amino acid at position 314 is Ala; an alteration comprising the amino acid at position 308 is Ile or Thr, the amino acid at position 309 is Pro, the amino acid at position 311 is Glu, Leu, or Ser, the amino acid at position 312 is Ala, and/or the amino acid at position 314 is Ala or Leu; and an alteration comprising the amino acid at position 308 is Thr, the amino acid at position 309 is Pro, the amino acid at position 311 is Ser, the amino acid at position 312 is Asp, and/or the amino acid at position 314 is Leu according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example:

an alteration comprising the amino acid at position 251 is Leu, the amino acid at position 252 is Tyr, the amino acid at position 254 is Ser or Thr, the amino acid at position 255 is Arg, and/or the amino acid at position 256 is Glu according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 428 is Leu, Met, Phe, Ser, or Thr, the amino acid at position 433 is Arg, Gln, His, Ile, Lys, Pro, or Ser, the amino acid at position 434 is His, Phe, or Tyr, and/or the amino acid at position 436 is Arg, Asn, His, Lys, Met, or Thr; and an alteration comprising the amino acid at position 428 is His or Met, and/or the amino acid at position 434 is His or Met according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 385 is Arg, the amino acid at position 386 is Thr, the amino acid at position 387 is Arg, and/or the amino acid at position 389 is Pro; and an alteration comprising the amino acid at position 385 is Asp, the amino acid at position 386 is Pro, and/or the amino acid at position 389 is Ser according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 250 is Gln or Glu; and an alteration comprising the amino acid at position 428 is Leu or Phe according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 250 is Gln, and/or the amino acid at position 428 is Leu or Phe; and an alteration comprising the amino acid at position 250 is Glu, and/or the amino acid at position 428 is Leu or Phe according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 307 is Gln and the amino acid at position 434 is Ala or Ser; an alteration comprising the amino acid at position 308 is Pro and the amino acid at position 434 is Ala; an alteration comprising the amino acid at position 252 is Tyr and the amino acid at position 434 is Ala; an alteration comprising the amino acid at position 378 is Val and the amino acid at position 434 is Ala; an alteration comprising the amino acid at position 428 is Leu and the amino acid at position 434 is Ala; an alteration comprising the amino acid at position 434 is Ala and the amino acid at position 436 is Ile; an alteration comprising the amino acid at position 308 is Pro and the amino acid at position 434 is Tyr; and an alteration comprising the amino acid at position 307 is Gln and the amino acid at position 436 is Ile according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 307 is Gln, the amino acid at position 380 is Ala, and the amino acid at position 434 is Ser; an alteration comprising the amino acid at position 307 is Gln, the amino acid at position 380 is Ala, and the amino acid at position 434 is Ala; an alteration comprising the amino acid at position 252 is Tyr, the amino acid at position 308 is Pro, and the amino acid at position 434 is Tyr; and an alteration comprising the amino acid at position 251 is Asp, the amino acid at position 307 is Gln, and the amino acid at position 434 is His according to EU numbering.

In addition to the above, alterations that can enhance the binding to human FcRn under an acidic pH range condition as compared to human IgG include, for example, at least one or more alterations selected from the following group:

an alteration comprising the amino acid at position 257 is Ile and the amino acid at position 311 is Ile; an alteration comprising the amino acid at position 257 is Ile and the amino acid at position 434 is His; and an alteration comprising the amino acid at position 376 is Val and the amino acid at position 434 is His according to EU numbering.

When an antigen-binding molecule of the present invention is produced using the Fc region of human IgG, an antigen-binding molecule containing the Fc region of IgG of the same subclass can be used as a control to assess the effect of the antigen-binding molecule of the present invention. Appropriate human IgG Fc regions that serve as a control include the Fc regions of human IgG1 (SEQ ID NO: 49, which results from adding A to the N terminus of RefSeq accession number AAC82527.1), human IgG2 (SEQ ID NO: 50, which results from adding A to the N terminus of RefSeq accession number AAB59393.1), human IgG3 (SEQ ID NO: 51, RefSeq accession number CAA27268.1), and human IgG4 (SEQ ID NO: 52, which results from adding A to the N terminus of RefSeq accession number AAB59394.1).

In mice, four types of Fcγ receptors have been identified: FcγRI (CD64), FcγRIIb (CD32), FcγRIII (CD16), and FcγRIV (CD16-2 or FcγRIII-2). As is the case in humans, FcγRIIb is believed to be the sole inhibitory Fcγ receptor. FcγRIIb1 and FcγRIIb2 are reported to be splicing variants of FcγRIIb. Both human and mouse FcγRIIb1 have a longer intracellular domain than FcγRIIb2. FcγRIIb1 is confirmed to be expressed in B cells. FcγRIIb2 is confirmed to be expressed in macrophages, mast cells, dendritic cells, basophils, neutrophils, and eosinophils (J. Clin. Immunol. (2005) 25 (1), 1-18).

To date, functional deficiency or reduced expression of FcγRIIb has been reported to have a correlation with the onset of autoimmune diseases in humans. For example, it has been reported that in some SLE patients, the binding of transcription activation factors is impaired due to the effect of genetic polymorphism in the expression promoter region of FcγRIIb, and the expression level of FcγRIIb is reduced (Hum. Genet. (2005) 117, 220-227; J. Immunol. (2004) 172, 7192-7199; J. Immunol. (2004) 172, 7186-7191). Furthermore, it has been reported that in some SLE patients, two types of genetic polymorphism of FcγRIIb are found in which the amino acid at position 233 is Ile or Thr. It has been reported that this site is located within the transmembrane domain of FcγRIIb, and in comparison to Ile, when the amino acid at position 233 is Thr, it becomes difficult for FcγRIIb to be present on lipid rafts, resulting in impairment of the signaling function of FcγRIIb (Nat. Med. (2005) 11, 1056-1058; Hum. Mol. Genet., (2005) 14, 2881-2892). Regarding mice, knockout C57BL/6 mice with the FcγRIIb gene disrupted have been reported to develop SLE-like symptoms such as autoantibody production and glomerulonephritis (Immunity 13 (2000) 277-285; J. Exp. Med. (2002) 195, 1167-1174). In addition, it has been reported that the expression level of FcγRIIb is reduced in mice that have been regarded as a spontaneous SLE onset model (Immunogenetics (2000) 51, 429-435; Int. Immunol. (1999) 11, 1685-1691; Curr. Biol. (2000) 10, 227-230; J. Immunol. (2002) 169, 4340-4346). These findings suggest that FcγRIIb regulates the humoral immunity in mice as is the case in humans.

When an antibody that has an Fc region of the present invention eliminates antigens via FcγRIIb, among the functions of FcγRIIb, the endocytotic function is thought to make the most important contribution. As described above, there are splicing variants of FcγRIIb: FcγRIIb1 and FcγRIIb2. It has been reported that the latter is primarily involved in the endocytosis of the immune complex between antibody and antigen (J. Immunol. (1994), 152 574-585; Science (1992) 256, 1808-1812; Cell (1989) 58, 317-327). To date, mouse FcγRIIb2 is reported to initiate endocytosis when incorporated into clathrin-coated pits (Cell (1989) 58, 317-327). Meanwhile, it has been reported that a dileucine motif is required for the FcγRIIb2-mediated endocytosis, and the dileucine motif is conserved in both humans and mice (EMBO J. (1994) 13 (13), 2963-2969). This finding also suggests that, like mouse, human FcγRIIb2 has endocytotic ability.

On the other hand, unlike FcγRIIb2, FcγRIIb1 is reported not to induce endocytosis. In its intracellular domain, FcγRIIb1 has an insertion sequence which is not found in FcγRIIb2. The sequence is believed to inhibit the incorporation of FcγRIIb1 into clathrin-coated pits, resulting in inhibition of endocytosis (J. Cell. Biol. (1992) 116, 875-888; J. Cell. Biol. (1989) 109, 3291-3302). As in mouse, human FcγRIIb1 contains the insertion sequence, and thus due to a similar mechanism, there expects to be a difference in the endocytotic ability of FcγRIIb1 and FcγRIIb2. Meanwhile, it has been reported that about 40% of the immune complexes on the cell surface are incorporated into cells in 20 minutes both in humans and in mice (Mol. Immunol. (2011) 49, 329-337; Science (1992) 256, 1808-1812). This finding suggests that in humans, FcγRIIb2 internalizes immune complexes into cells at a rate similar to that in mice.

In the Fcγ receptor family, FcγRIIb alone has ITIM inside the cell in both mice and humans, and the distribution of cells expressing FcγRIIb is identical. Thus, its function in the immunological regulation is also assumed to be the same. Furthermore, in light of the fact that immune complexes are taken up into cells at the same rate in humans and mice, the effect of FcγRIIb-mediated antigen elimination by antibody in human is expected to be predictable by using mice. In fact, as shown in the Examples discussed below, as compared to when mIgG1 is administered, antigen clearance is increased when altered molecules (mF44 and mF46) with increased affinity for mouse FcγRIIb and FcγRIII relative to mIgG1 are administered to normal mice.

Furthermore, as shown in the Examples described below, similar experiments were carried out using Fc receptor γ chain-deficient mice. As for mice, it has been reported that FcγRs other than FcγRIIb are expressed only in the co-presence of the γ chain. For this reason, Fc receptor γ chain-deficient mice express FcγRIIb alone. The effect on antigen elimination produced when the binding activity to FcγRIIb is selectively increased can be studied by administering mF44 and mF46 to Fc receptor γ chain-deficient mice. The results described in the Examples demonstrate that mF44 and mF46 administered to Fc receptor γ chain-deficient mice increase antigen clearance as compared to when mIgG1 is administered to the same mice. Furthermore, the results described in the Examples demonstrate that even when administered to Fc receptor γ chain-deficient mice, mF44 and mF46 eliminate antigens to almost the same level as that when administered to normal mice.

Furthermore, as shown in the Examples described below, similar experiments were carried out using FcγRIII-deficient mice. mIgG1, mF44, and mF46 bind to only FcγRIIb and FcγRIII among mouse FcγRs. For this reason, the effect on antigen elimination produced when the binding activity to FcγRIIb is selectively increased can be studied by administering these antibodies to FcγRIII-deficient mice. The results described in the Examples demonstrate that when administered to FcγRIII-deficient mice, mF44 and mF46 increase antigen clearance as compared to when mIgG1 is administered to the same mice. Furthermore, the results described in the Examples demonstrate that even when administered to FcγRIII-deficient mice, mF44 and mF46 eliminate antigens to almost the same level as that when administered to normal mice or Fc receptor γ chain-deficient mice.

The results described above reveals that antigen elimination can be accelerated by increasing the binding activity in an FcγRIIb-selective manner without increasing the binding activity to activating Fcγ receptors.

In addition to previous literature reports studied above, the results of studies using mice described above suggest that as is the case in mouse, FcγRIIb-mediated intake of immune complexes into cells occurs in humans, and as a result, antibodies that have an Fc region with increased binding activity to human FcγRIIb in a selective manner can accelerate antigen elimination. Furthermore, as discussed above, since the rate of FcγRIIb-mediated intake of immune complexes into cells is assumed to be comparable between mouse and human, the antigen elimination-accelerating effect comparable to that of antibodies having an Fc region with increased affinity for mouse FcγRIIb can be achieved with antibodies that have an Fc region with increased affinity for human FcγRIIb.

In general, the Kabat numbering system is used to describe residues in the antibody variable regions (roughly, the residues at positions 1 to 107 in the light chain, and the residues at positions 1 to 113 in the heavy chain) (for example, Kabat et al., Sequences of Proteins of Immunological Interest. 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)). “The EU numbering system” or “EU index” is generally used when referring to residues in the heavy chain constant region of an antibody (for example, the EU index reported in Kabat et al., supra). “The EU index of Kabat” refers to residue numbering for human IgG1 EU antibody. In the present specification, unless otherwise specified, the residue numbers in antibody variable regions are described using the Kabat numbering system. In the present specification, unless otherwise specified, the residue numbers in antibody constant regions are described using the EU numbering system (see, for example, WO2006/073941).

Antigen-binding domains of the present invention have antigen-binding activity which is different between intracellular condition and extracellular condition. Intracellular condition and extracellular condition refer to conditions that are different between in and outside of the cell. Categories of conditions include, for example, ion concentration, more specifically, hydrogen ion concentration (pH) and calcium ion concentration. Intracellular condition preferably refers to an environment characteristic to the environment inside the endosome, while extracellular condition preferably refers to an environment characteristic to the environment in plasma.

Antigen-binding domains with the property of having an antigen-binding activity that changes according to ion concentration can be obtained by screening a large number of antigen-binding domains for domains having such property. For example, when antigen-binding molecules of the present invention are antibodies, antibodies with the above-described property can be obtained by producing a large number of antibodies whose sequences are different from one another by a hybridoma method or an antibody library method and measuring their antigen-binding activities at different ion concentrations. The B cell cloning method illustrated in Example 1 of the present specification is particularly suitable as a method of screening for such antibodies. Furthermore, as described below, at least one distinctive amino acid residue that can confer an antigen-binding domain with the property of having an antigen-binding activity that changes according to ion concentration is specified, to prepare as a library of a large number of antigen-binding domains that have different sequences while sharing the distinctive amino acid residues as a common structure. Such a library can be screened to efficiently isolate antigen-binding domains that have the property described above.

In an embodiment of the present invention, the condition of ion concentrations refers to the condition of hydrogen ion concentrations or pH condition. In the present invention, the concentration of proton. i.e., the nucleus of hydrogen atom, is treated as synonymous with hydrogen ion concentration index (pH). When the activity of hydrogen ion in an aqueous solution is represented as aH+, pH is defined as −log 10aH+. When the ionic strength of the aqueous solution is low (for example, lower than 10⁻³), aH+ is nearly equal to the hydrogen ion strength. For example, the ionic product of water at 25° C. and 1 atmosphere is Kw=aH+aOH=10⁻¹⁴, and therefore in pure water, aH+=aOH=10⁻⁷. In this case, pH=7 is neutral; an aqueous solution whose pH is lower than 7 is acidic or whose pH is greater than 7 is alkaline.

In the present invention, when the pH condition is used as the ion concentration condition, it is desirable that the antigen-binding activity under an acidic pH range (i.e., a high hydrogen ion concentration or low pH) condition is lower than that under a neutral pH range (i.e., a low hydrogen ion concentration or high pH) condition.

Intracellular pH is acidic as compared to extracellular pH. Conversely, extracellular pH is neutral as compared to intracellular pH. The present invention provides antigen-binding molecules in which the extracellular condition is a neutral pH range condition and the intracellular condition is an acidic pH range condition. In the present invention, the acidic pH range is preferably pH 4.0 to pH 6.5, more preferably pH 5.0 to pH 6.5, still more preferably any of pH 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, and 6.5, and particularly preferably pH 5.8 to pH 6.0 which is close to the pH in the early endosome in vivo. Meanwhile, in the present invention, the neutral pH range is preferably pH 6.7 to pH 10.0, more preferably pH 7.0 to pH 9.0, still more preferably any of pH 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0, and particularly preferably pH 7.4 which is close to the pH in plasma (in blood).

When the level of antigen-binding activity is compared between the acidic pH range condition and the neutral pH range condition, it is preferable that the binding of antigen-binding domains of the present invention is stronger under a neutral pH range condition than under an acidic pH range condition. When the level of binding activity is expressed with the dissociation constant (KD), the value of KD (acidic pH)/KD (neutral pH) is preferably 2 or more, more preferably 10 or more, and still more preferably 40 or more. The upper limit of the value of KD (acidic pH)/KD (neutral pH) is not particularly limited, and may be any value such as 100, 400, 1000, or 10000, as long as it can be produced with the techniques of skilled artisans. It is possible to use the dissociation rate constant (kd) instead of KD. When it is difficult to calculate the KD value, the activity may be assessed based on the level of binding response in Biacore when analytes are passed at the same concentration. When antigens are passed over a chip immobilized with antigen-binding molecules of the present invention, the binding response under an acidic pH range condition is preferably ½ or less of the binding response under a neutral pH range condition, more preferably ⅓ or less, still more preferably ⅕ or less, and particularly preferably 1/10 or less.

It is known that in general the in vivo extracellular pH (for example, in plasma) is neutral while the intracellular pH (for example, in the endosome) is acidic. When the property of having a lower antigen-binding activity under an intracellular pH condition than under an extracellular pH condition is conferred to the antigen-binding domain of antigen-binding molecules of the present invention, antigens that have bound to the antigen-binding molecule of the present invention outside of the cell dissociate from the antigen-binding molecule of the present invention inside the cell, thereby enhancing antigen incorporation into the cell from the outside of the cell. Such antigen-binding molecules, when administered to the living body, can reduce antigen concentration in plasma and thereby reduce the physiological activity of antigens in vivo. Thus, antigen-binding molecules of the present invention are useful.

Methods for conferring to antigen-binding domains of the present invention the property of binding more weakly to antigens under an acidic pH range condition than binding under a neutral pH range condition are not particularly limited, and the property may be conferred by any methods. Specifically, the methods are described in WO2009/125825, and include a method of substituting at least one amino acid residue with histidine and/or inserting at least one histidine in an antigen-binding domain. In a preferred embodiment, the antigen-binding molecules of the present invention contain a substitution of at least one amino acid residue by histidine and/or an insertion of at least one histidine in their antigen-binding domain. It is already known that the pH-dependent antigen-binding activity can be conferred to antibodies by substituting their amino acid residues with histidine (Ito W et al., FEBS Lett. (1992) 309, 85-88). The site of histidine substitution and/or insertion is not particularly limited, and amino acid residues at any positions may be substituted with histidine, and histidine may be inserted at any sites as long as the antigen-binding activity under an acidic pH range condition is reduced to be lower than that under a neutral pH range condition. Histidine substitution and/or insertion sites preferably include, for example, the site to which an antigen directly binds and portions that contribute to the preservation of the conformation of the site. For example, when the antigen-binding domain is an antibody variable region, the sites include CDRs and regions that contribute to the preservation of their conformation. Specifically, the sites include H27, H31, H32, H33, H35, H50, H58, H59, H61, H62. H63, H64, H65, H99, H100b, and H102 in the heavy chain: and L24, L27, L28, L32. L53, L54, L56, L90, L92, and L94 in the light chain. Among these sites, H32, H61, L53, L90, and L94 are expected to be high in universality (the positions of amino acid residues are indicated according to Kabat numbering (Kabat E A et al., 1991. Sequences of Proteins of Immunological Interest. NIH)). Preferred combinations of substituting multiple sites with histidine include, for example, the combination of H27, H31, and H35; the combination of H27, H31, H32, H35, H58, H62, and H102; the combination of L32 and L53; and the combination of L28, L32, and L53. Furthermore, preferred combinations of substitution sites in the heavy chain and light chain include, for example, the combination of H27, H31, L32, and L53.

Histidine is substituted and/or inserted at random into the antigen-binding domains of antigen-binding molecules of the present invention by a method such as histidine scanning, where histidine is used instead of alanine in an alanine scanning method known to those skilled in the art. It is possible to select from the resulting molecules, antigen-binding domains that bind more weakly to antigens under an acidic pH range condition than under a neutral pH range condition.

The number of histidines to be substituted and/or inserted can be appropriately determined by those skilled in the art. Histidine may be substituted or inserted at only one site. Alternatively, histidine may be substituted or inserted at two or more sites. Alternatively, histidine substitution and histidine insertion may be combined at two or more sites.

It is preferable that the antigen-binding domains have comparable antigen-binding activities before and after histidine substitution and/or insertion. Herein, comparable activity means 10% or more, preferably 30% or more, more preferably 50% or more, still more preferably 80% or more, and particularly preferably 90% or more of the original activity.

When antigen-binding molecules provided by the present invention contain the antibody constant region, methods for conferring to the antigen-binding provided by the present invention the property of binding more weakly to the antigen under an acidic pH range condition than under a neutral pH range condition include methods for altering the antibody constant region. Methods for altering the antibody constant region include, for example, methods in which the constant region is compared among isotypes (IgG1, IgG2, IgG3, and IgG4) to select an isotype with reduced antigen-binding activity under an acidic pH range condition (dissociation rate is accelerated under an acidic pH range condition). Such methods also include methods that reduce the antigen binding activity under an acidic pH range condition (dissociation rate is accelerated under an acidic pH range condition) by introducing amino acid alteration into the amino acid sequence of an isotype (IgG1, IgG2, IgG3, or IgG4). The sequence of the hinge domain of an antibody constant region varies considerably among isotypes (IgG1, IgG2, IgG3, and IgG4). The difference in the amino acid sequence of the hinge domain has great effects on the antigen-binding activity. Thus, the antigen-binding activity under an acidic pH range condition can be reduced by selecting an isotype appropriate for the type of binding antigen. Meanwhile, when an amino acid alteration is introduced into the amino acid sequence of an isotype, the site of introducing an amino acid alteration is preferably within the hinge domain.

A large number of antigen-binding domains is prepared as a library, in which the antigen-binding domains have different sequences while sharing as a common structure the above-described amino acid residues that change the antigen-binding activity according to the hydrogen ion concentration. The library can be screened to efficiently obtain antigen-binding domains with binding activity to a desired antigen, and in which their antigen-binding activity changes according to the hydrogen ion concentration.

For example, a light chain variable region with a framework sequence containing at least one amino acid residue that changes the antigen-binding activity according to the hydrogen ion concentration can be combined with a heavy chain variable region containing a random sequence, to construct a library that contains multiple antigen-binding domains that have different sequences while sharing as a common structure amino acid residues that change the antigen-binding activity according to the hydrogen ion concentration. In a preferred embodiment where such amino acid residues are introduced into the light chain altered region, the amino acid residues may be contained in the CDR1 of the light chain altered region, more preferably at positions 24, 27, 28, 31, 32, and/or 34 according to Kabat numbering in the CDR1 of the light chain variable region. In another preferred embodiment, the amino acid residues may be contained in the CDR2 of the light chain variable region, more preferably at positions 50, 51, 52, 53, 54, 55, and/or 56 according to Kabat numbering in the CDR2 of the light chain variable region. In still another preferred embodiment, the amino acid residues may be contained in the CDR3 of the light chain variable region, more preferably at positions 89, 90, 91, 92, 93, 94, and/or 95A according to Kabat numbering in the CDR3 of the light chain variable region. The amino acid residues may be contained alone, or two or more may be contained in combination as long as they change the antigen-binding activity according to the hydrogen ion concentration.

When the light chain variable region containing at least one amino acid residue that changes the antigen-binding activity according to the hydrogen ion concentration is combined with the heavy chain variable region containing a random sequence to produce an antigen-binding domain, it is possible to design it in such a way that its light chain variable region further contains flexible residues. Such flexible residues are not particularly limited in number and position, as long as the antigen-binding activity of the antigen-binding domain of the present invention is changed according to the hydrogen ion concentration. Specifically, the light chain CDR sequences and/or FR sequences may contain one or more flexible residues. Without being particularly limited thereto, flexible residues that are introduced into the sequence of the light chain variable region include, for example, amino acid residues shown in Tables 7 and 8. Meanwhile, without being particularly limited thereto, the sequence of the light chain variable region, other than flexible residues and amino acid residues that change the antigen-binding activity according to the hydrogen ion concentration, preferably includes germ-line sequences such as Vk1 (SEQ ID NO: 58), Vk2 (SEQ ID NO: 59), Vk3 (SEQ ID NO: 60), and Vk4 (SEQ ID NO: 61).

TABLE 7 POSITION AMINO ACID CDR1 28 S: 100% 29 I: 100% 30 N: 25% S: 25% R: 25% H: 25% 31 S: 100% 32 H: 100% 33 L: 100% 34 A: 50% N: 50% CDR2 50 H: 100% OR A: 25% D: 25% G: 25% K: 25% 51 A: 100% A: 100% 52 S: 100% S: 100% 53 K: 33.3% N: 33.3% S: 33.3% H: 100% 54 L: 100% L: 100% 55 Q: 100% Q: 100% 56 S: 100% S: 100% CDR3 90 Q: 100% OR Q: 100% 91 H: 100% S: 33.3% R: 33.3% Y: 33.3% 92 G: 25% N: 25% S: 25% Y: 25% H: 100% 93 H: 33.3% N: 33.3% S: 33.3% H: 33.3% N: 33.3% S: 33.3% 94 S: 50% Y: 50% S: 50% Y: 50% 95 P: 100% P: 100% 96 L: 50% Y: 50% L: 50% Y: 50% (“POSITION” indicates Kabat numbering)

TABLE 8 CDR POSITION AMINO ACID CDR1 28 S: 100% 29 I: 100% 30 H: 30% N: 10% S: 50% R: 10% 31 N: 35% S: 65% 32 H: 40% N: 20% Y: 40% 33 L: 100% 34 A: 70% N: 30% CDR2 50 A: 25% D: 15% G: 25% H: 30% K: 5% 51 A: 100% 52 S: 100% 53 H: 30% K: 10% N: 15% S: 45% 54 L: 100% 55 Q: 100% 56 S: 100% CDR3 90 Q: 100% 91 H: 30% S: 15% R: 10% Y: 45% 92 G: 20% H: 30% N: 20% S: 15% Y: 15% 93 H: 30% N: 25% S: 45% 94 S: 50% Y: 50% 95 P: 100% 96 L: 50% Y: 50% (“POSITION” indicates Kabat numbering)

Any amino acid residues may be suitably used as an amino acid residue that changes the antigen-binding activity according to the hydrogen ion concentration. Specifically, such amino acid residues include those with a side-chain pKa of 4.0 to 8.0. Such electron-donating amino acids preferably include, for example, native amino acids such as histidine and glutamic acid, and unnatural amino acids such as histidine analogs (US20090035836), m-N02-Tyr (pKa 7.45), 3,5-Br2-Tyr (pKa 7.21), and 3.5-I2-Tyr (pKa 7.38) (Bioorg. Med. Chem. (2003) 11 (17), 3761-2768). The amino acid residues particularly preferably include, for example, those with a side-chain pKa of 6.0 to 7.0. Such electron-donating amino acids preferably include, for example, histidine.

Furthermore, in one embodiment of the present invention, the ion concentration refers to a metal ion concentration. “Metal ions” refer to ions of group I elements except hydrogen such as alkaline metals and copper group elements, group II elements such as alkaline earth metals and zinc group elements, group III elements except boron, group IV elements except carbon and silicon, group VIII elements such as iron group and platinum group elements, elements belonging to subgroup A of groups V, VI, and VII, and metal elements such as antimony, bismuth, and polonium. Metal atoms have the property of releasing valence electrons to become cations. This is referred to as ionization tendency. Metals with strong ionization tendency are deemed to be chemically active.

In the present invention, preferred metal ions include, for example, calcium ion. Calcium ion is involved in modulation of many biological phenomena, including contraction of muscles such as skeletal, smooth, and cardiac muscles; activation of movement, phagocytosis, and the like of leukocytes; activation of shape change, secretion, and the like of platelets; activation of lymphocytes; activation of mast cells including secretion of histamine; cell responses mediated by catecholamine a receptor or acetylcholine receptor; exocytosis; release of transmitter substances from neuron terminals; and axoplasmic flow in neurons. Known intracellular calcium ion receptors include troponin C, calmodulin, parvalbumin, and myosin light chain, which have several calcium ion-binding sites and are believed to be derived from a common origin in terms of molecular evolution. There are also many known calcium-binding motifs. Such well-known motifs include, for example, cadherin domains, EF-hand of calmodulin, C2 domain of Protein kinase C. Gla domain of blood coagulation protein Factor IX, C-type lectins of acyaroglycoprotein receptor and mannose-binding receptor, A domains of LDL receptors, annexin, thrombospondin type 3 domain, and EGF-like domains.

In the present invention, when the metal ion is calcium ion, it is desirable that the antigen-binding activity is lower under a low calcium ion concentration condition than under a high calcium ion concentration condition.

Meanwhile, the intracellular calcium ion concentration is lower than the extracellular calcium ion concentration. Conversely, the extracellular calcium ion concentration is higher than the intracellular calcium ion concentration. In the present invention, the low calcium ion concentration is preferably 0.1 μM to 30 μM, more preferably 0.5 μM to 10 μM, and particularly preferably 1 μM to 5 μM which is close to the calcium ion concentration in the early endosome in vivo. Meanwhile, in the present invention, the high calcium ion concentration is preferably 100 μM to 10 mM, more preferably 200 μM to 5 mM, and particularly preferably 0.5 mM to 2.5 mM which is close to the calcium ion concentration in plasma (in blood). In the present invention, it is preferable that the low calcium ion concentration is the calcium ion concentration in endosomes, and the high calcium ion concentration is the calcium ion concentration in plasma.

When the level of antigen-binding activity is compared between low and high calcium ion concentrations, it is preferable that the binding of antigen-binding domains of the present invention is stronger at a high calcium ion concentration than at a low calcium ion concentration. In other words, it is preferable that the antigen-binding activity of antigen-binding domains of the present invention is lower at a low calcium ion concentration than at a high calcium ion concentration.

When the level of binding activity is expressed with the dissociation constant (KD), the value of KD (low calcium ion concentration)/KD (high calcium ion concentration) is greater than 1, preferably 2 or more, still more preferably 10 or more, and yet more preferably 40 or more. The upper limit of the value of KD (low calcium ion concentration)/KD (high calcium ion concentration) is not particularly limited, and may be any value such as 100, 400, 1000, or 10000, as long as it can be produced with the techniques of skilled artisans. It is possible to use the dissociation rate constant (kd) instead of KD. When it is difficult to calculate the KD value, the activity may be assessed based on the level of binding response in Biacore when analytes are passed at the same concentration. When antigens are passed over a chip immobilized with antigen-binding molecules of the present invention, the binding response at a low calcium concentration is preferably ½ or less of the binding response at a high calcium concentration, more preferably ⅓ or less, still more preferably ⅕ or less, and particularly preferably 1/10 or less.

It is known that in general the in vivo extracellular calcium ion concentration (for example, in plasma) is high, and the intracellular calcium ion concentration (for example, in the endosome) is low. Thus, in the present invention, it is preferable that the extracellular condition is a high calcium ion concentration, and the intracellular condition is a low calcium ion concentration.

When the property that the antigen-binding activity is lower under an intracellular calcium ion concentration condition than under an extracellular calcium ion concentration condition is conferred to the antigen-binding domain of antigen-binding molecules of the present invention, antigens that have bound to antigen-binding molecule of the present invention outside of the cell dissociate from the antigen-binding molecule of the present invention inside the cell, thereby enhancing antigen incorporation into the cell from the outside of the cell. Such antigen-binding molecules, when administered to the living body, can reduce antigen concentration in plasma and reduce the physiological activity of antigens in vivo. Thus, antigen-binding molecules of the present invention are useful.

Methods of screening for antigen-binding domains or antigen-binding molecules having a lower antigen-binding activity under a low calcium ion concentration condition than under a high calcium ion concentration condition include, for example, the method described in WO2012/073992 (for example, paragraphs 0200-0213).

Methods for conferring antigen-binding domains of the present invention with the property of binding more weakly to antigens under a low calcium ion concentration condition than under a high calcium ion concentration condition are not particularly limited, and may be carried out by any methods. Specifically, the methods are described in Japanese Patent Application No. 2011-218006 and include, for example, methods for substituting at least one amino acid residue in an antigen-binding domain with an amino acid residue having metal chelating activity, and/or inserting into an antigen-binding domain at least one amino acid residue having metal chelating activity. Antigen-binding molecules of the present invention in which at least one amino acid residue of the antigen-binding domain has been substituted with an amino acid residue having metal chelating activity and/or at least one amino acid residue having metal chelating activity has been inserted into the antigen-binding domain are a preferred embodiment of antigen-binding molecules of the present invention. Amino acid residues having metal chelating activity preferably include, for example, serine, threonine, asparagine, glutamine, aspartic acid, and glutamic acid.

Furthermore, amino acid residues that change the antigen-binding activity of antigen-binding domains according to the calcium ion concentration preferably include, for example, amino acid residues that form a calcium-binding motif. Calcium-binding motifs are well known to those skilled in the art, and have been described in detail (for example, Springer et al., (Cell (2000) 102, 275-277); Kawasaki and Kretsinger (Protein Prof. (1995) 2, 305-490); Moncrief et al., (J. Mol. Evol. (1990) 30, 522-562); Chauvaux et al., (Biochem. J. (1990) 265, 261-265); Bairoch and Cox (FEBS Lett. (1990) 269, 454-456); Davis (New Biol. (1990) 2, 410-419); Schaefer et al., (Genomics (1995) 25, 638 to 643); Economou et al., (EMBO J. (1990) 9, 349-354); Wurzburg et al., (Structure. (2006) 14, 6, 1049-1058)). EF hand in troponin C, calmodulin, parvalbumin, and myosin light chain; C2 domain in protein kinase C; Gla domain in blood coagulation protein factor IX; C-type lectin of acyaroglycoprotein receptor and mannose-binding receptor, ASGPR, CD23, and DC-SIGN; A domain in LDL receptor; annexin domain; cadherin domain; thrombospondin type 3 domain; and EGF-like domain are preferably used as calcium-binding motifs. In addition to the above, the calcium-binding motif in the antigen-binding domain of SEQ ID NO: 57 is preferably used.

Antigen-binding domains of the present invention can contain amino acid residues that change the antigen-binding activity according to the calcium ion concentration, such as the above-described amino acid residues with metal chelating activity and amino acid residues that form a calcium-binding motif. The location of such amino acid residues in the antigen-binding domain is not particularly limited, and they may be located at any position as long as the antigen-binding activity changes according to the calcium ion concentration. Meanwhile, such amino acid residues may be contained alone or in combination of two or more, as long as the antigen-binding activity changes according to the calcium ion concentration. The amino acid residues preferably include, for example, serine, threonine, asparagine, glutamine, aspartic acid, and glutamic acid. When an antigen-binding domain is an antibody variable region, the amino acid residues may be contained in the heavy chain variable region and/or the light chain variable region. In a preferred embodiment, the amino acid residues may be contained in the CDR3 of the heavy chain variable region, more preferably at positions 95, 96, 100a, and/or 101 according to Kabat numbering in the CDR3 of the heavy chain variable region.

In another preferred embodiment, the amino acid residues may be contained in the CDR1 of the light chain variable region, more preferably at positions 30, 31, and/or 32 according to Kabat numbering in the CDR1 of the light chain variable region. In still another preferred embodiment, the amino acid residues may be contained in the CDR2 of the light chain variable region, more preferably at position 50 according to Kabat numbering in the CDR2 of the light chain variable region. In yet another preferred embodiment, the amino acid residues may be contained in the CDR3 of the light chain variable region, more preferably at position 92 according to Kabat numbering in the CDR3 of the light chain variable region.

Furthermore, it is possible to combine the above-described embodiments. For example, the amino acid residues may be contained in two or three CDRs selected from the CDR1, CDR2, and CDR3 of the light chain variable region, more preferably at any one or more of positions 30, 31, 32, 50, and/or 92 according to Kabat numbering in the light chain variable region.

A large number of antigen-binding domains that have different sequences while sharing as a common structure the above-described amino acid residues that change the antigen-biding activity according to the calcium ion concentration are prepared as a library. The library can be screened to efficiently obtain antigen-binding domains with binding activity to a desired antigen, in which their antigen-binding activity changes according to the calcium ion concentration.

When the antigen-binding domain is an antibody variable region, in a particularly preferred embodiment, it is desirable that the framework sequences of the light chain and/or heavy chain variable region have a human germ-line framework sequence. Thus, in an embodiment of the present invention, when the framework sequence is completely a human sequence, the antigen-binding domain of the present invention, when administered to humans (for example, to treat diseases), is expected to induce little or no immunogenic response. In this context, herein, “having a germ-line sequence” means that a portion of the framework sequence of the present invention is identical to a portion of a human germ-line framework sequence. For example, even when an antigen-binding domain of the present invention has a sequence resulting from combining multiple different human germ-line framework sequences, it is an antigen-binding domain of the present invention “having a germ-line sequence”.

Without being bound by a particular theory, one reason why the use of a germ-line sequence is expected to result in the elimination of adverse immune responses in most individuals is believed to be as follows. As a result of the process of affinity maturation during normal immune responses, somatic cell mutations occur frequently in the variable region of immunoglobulins. Such mutations also affect residues in the framework region while they primarily occur around CDRs of which sequences are hypervariable. There is no such framework mutation in the germ line sequences, and thus they can be immunogenic in patients. On the other hand, the normal human population is exposed to most framework sequences expressed from the germ line genes. As a result of immunotolerance, the germ line sequences are expected to be only weakly immunogenic or nonimmunogenic in patients. To maximize the possibility of immunotolerance, genes encoding the variable region can be selected from a group of functional germ-line genes (which are expressed normally).

The framework preferably includes, for example, currently known framework region sequences that are completely of the human type. The sequences of such framework regions are shown, for example, on the websites of V-Base (http://vbase.mrc-cpe.cam.ac.uk/). Those framework region sequences can be appropriately used as a germ line sequence contained in an antigen-binding domain of the present invention. The germ line sequences may be categorized according to their similarity (Tomlinson et al. (J. Mol. Biol. (1992) 227, 776-798); Williams and Winter (Eur. J. Immunol. (1993) 23, 1456-1461); Cox et al. (Nat. Genetics (1994) 7, 162-168)). Appropriate germ line sequences can be selected from Vκ, which is grouped into seven subgroups; Vλ, which is grouped into ten subgroups; and VH, which is grouped into seven subgroups.

Fully human VH sequences preferably include, but are not limited to, for example, VH sequences of:

subgroup VH1 (for example, VH1-2, VH1-3, VH1-8, VH1-18, VH1-24, VH1-45, VH1-46, VH1-58, and VH1-69); subgroup VH2 (for example, VH2-5, VH2-26, and VH2-70); subgroup VH3 (VH3-7, VH3-9, VH3-11, VH3-13, VH3-15, VH3-16, VH3-20, VH3-21, VH3-23, VH3-30, VH3-33, VH3-35, VH3-38, VH3-43, VH3-48, VH3-49, VH3-53, VH3-64, VH3-66, VH3-72, VH3-73, and VH3-74): subgroup VH4 (VH4-4, VH4-28, VH4-31, VH4-34, VH4-39, VH4-59, and VH4-61); subgroup VH5 (VH5-51); subgroup VH6 (VH6-1); and subgroup VH7 (VH7-4 and VH7-81). These are also described in known documents (Matsuda et al. (J. Exp. Med. (1998) 188, 1973-1975)) and such, and thus persons skilled in the art can appropriately design antigen-binding domains of the present invention based on the information of these sequences. It is also preferable to use other fully human framework regions or framework sub-regions.

Fully human VK sequences preferably include, but are not limited to, for example:

A20, A30, L1, L4, L5, L8, L9, L11, L12, L14, L15, L18, L19, L22, L23, L24, O2, O4, O8, O12, O14, and O18, grouped into subgroup Vk1; A1, A2, A3, A5, A7, A17, A18, A19, A23, O1, and O11, grouped into subgroup Vk2; A11, A27, L2, L6, L10, L16, L20, and L25, grouped into subgroup Vk3; B3, grouped into subgroup Vk4; B2 (herein also referred to as Vk5-2), grouped into subgroup Vk5; and A10, A14, and A26, grouped into subgroup VK6 (Kawasaki et al. (Eur. J. Immunol. (2001) 31, 1017-1028); Schable and Zachau (Biol. Chem. Hoppe Seyler (1993) 374, 1001-1022); Brensing-Kuppers et al. (Gene (1997) 191, 173-181)).

Fully human VL sequences preferably include, but are not limited to, for example:

V1-2, V1-3, V1-4, V1-5, V1-7, V1-9, V1-11, V1-13, V1-16, V1-17, V1-18, V1-19, V1-20, and V1-22, grouped into subgroup VL1; V2-1, V2-6, V2-7, V2-8, V2-11, V2-13, V2-14, V2-15, V2-17, and V2-19, grouped into subgroup VL1; V3-2, V3-3, and V3-4, grouped into subgroup VL3; V4-1, V4-2, V4-3, V4-4, and V4-6, grouped into subgroup VL4; and V5-1, V5-2, V5-4, and V5-6, grouped into subgroup VL5 (Kawasaki et al. (Genome Res. (1997) 7, 250-261)).

Normally, these framework sequences are different from one another at one or more amino acid residues. These framework sequences can be used in combination with at least one amino acid residue that alters the antigen-binding activity depending on ion concentrations described above. Other examples of frameworks include, but are not limited to, for example, KOL, NEWM, REI, EU, TUR, TEI, LAY, and POM (for example, Kabat et al. (1991) supra; Wu et al. (J. Exp. Med. (1970) 132, 211-250)).

For example, a light chain variable region that contains in its framework sequence at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration can be combined with a heavy chain variable region containing a random sequence to construct a library containing a number of antigen-binding domains that have different sequences while sharing as a common structure the amino acid residues that change the antigen-binding activity according to the calcium ion concentration. Without being particularly limited thereto, a preferred example includes a library of antigen-binding domains resulting from combining the heavy chain variable region containing a random sequence with the light chain variable region that belongs to the Vk5-2 family such as SEQ ID NO: 57 (Vk5-2). Preferred examples also include a library of antigen-binding domains resulting from combining the heavy chain variable region containing a random sequence with the sequence of a light chain variable region in which at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration has been substituted for specific amino acid residues in a germ-line sequence such as SEQ ID NO: 58 (Vk1), SEQ ID NO: 59 (Vk2), SEQ ID NO: 60 (Vk3), and SEQ ID NO: 61 (Vk4).

Furthermore, it is possible to design in such a way that flexible residues are contained in the light chain variable region of which framework sequences contain at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration. Such flexible residues are not particularly limited in number and position as long as the antigen-binding activity of antigen-binding domains of the present invention changes according to the ion concentration. Specifically, the CDR and/or FR sequences of the heavy chain variable region and/or the light chain variable region may contain one or more flexible residues. Without being particularly limited thereto, flexible residues that are introduced into the light chain variable region of SEQ ID NO: 57 (Vk5-2) include, for example, amino acid residues shown in Tables 9 and 10.

TABLE 9 Kabat CDR NUMBERING 70% AMINO ACID OF THE TOTAL CDR1 28 S: 100% 29 I: 100% 30 E: 72% N: 14% S: 14% 31 D: 100% 32 D: 100% 33 L: 100% 34 A: 70% N: 30% CDR2 50 E: 100% 51 A: 100% 52 S: 100% 53 H: 5% N: 25% S: 45% T: 25% 54 L: 100% 55 Q: 100% 56 S: 100% CDR3 90 Q: 100% 91 H: 25% S: 15% R: 15% Y: 45% 92 D: 80% N: 10% S: 10% 93 D: 5% G: 10% N: 25% S: 50% R: 10% 94 S: 50% Y: 50% 95 P: 100% 96 L: 50% Y: 50%

TABLE 10 Kabat CDR NUMBERING 30% AMINO ACID OF THE TOTAL CDR1 28 S: 100% 29 I: 100% 30 E: 83% S: 17% 31 D: 100% 32 D: 100% 33 L: 100% 34 A: 70% N: 30% CDR2 50 H: 100% 51 A: 100% 52 S: 100% 53 H: 5% N: 25% S: 45% T: 25% 54 L: 100% 55 Q: 100% 56 S: 100% CDR3 90 Q: 100% 91 H: 25% S: 15% R: 15% Y: 45% 92 D: 80% N: 10% S: 10% 93 D: 5% G: 10% N: 25% S: 50% R: 10% 94 S: 50% Y: 50% 95 P: 100% 96 L: 50% Y: 50%

Herein, flexible residue refers to an amino acid residue that is present at a position where the type of amino acid varies greatly in the light chain variable regions and heavy chain variable regions when comparing the amino acid sequences of known and/or native antibodies or antigen-binding domains. The positions that vary greatly are generally present in the CDR regions. For example, the data provided as Kabat, Sequences of Proteins of Immunological Interest (National Institute of Health Bethesda Md.) (1987 and 1991) is useful to determine the positions that vary greatly in known and/or native antibodies. Furthermore, various databases on the Internet (http://vbase.mrc-cpe.cam.ac.uk/, http://www.bioinf.org.uk/abs/index.html) provide the collected sequences of many human light chains and heavy chains. The sequence information is useful for determining the positions that vary greatly in the present invention. In the present invention, when at a certain amino acid position, the number of possible variations of amino acids is preferably about 2 to 20, preferably about 3 to 19, preferably about 4 to 18, preferably 5 to 17, preferably 6 to 16, preferably 7 to 15, preferably 8 to 14, preferably 9 to 13, and preferably 10 to 12, such a position is defined as varying greatly. Meanwhile, at a certain position, the number of possible variations of amino acids can be preferably at least about 2, preferably at least about 4, preferably at least about 6, preferably at least about 8, preferably at least about 10, and preferably at least about 12.

In order to produce an antigen-binding domain, when a light chain variable region containing at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration is combined with a heavy chain variable region containing a random sequence, it is possible to design it in such a way that its light chain variable region further contains flexible residues. The flexible residues are not particularly limited in number and position as long as the antigen-binding activity changes according to the calcium ion concentration. Specifically, the light chain CDR sequences and/or FR sequences may contain one or more flexible residues. Without being particularly limited, flexible residues that are introduced into the light chain variable region include, for example, amino acid residues shown in Tables 9 and 10.

In the present invention, known methods can be appropriately combined to prepare as a randomized variable region library the heavy chain and/or the light chain variable region that have a random sequence. In an embodiment, immune libraries constructed based on antibody genes derived from the lymphocytes of animals immunized with a specific antigen, humans whose antibody titer in blood has been increased due to vaccination, patients with infection, cancer patients, autoimmune disease patients, and such may be suitably used as a randomized variable region library.

In another embodiment, a synthetic library in which arbitrary CDR sequences of V genes from genomic DNA or functional reshaped V genes are replaced with a set of synthetic oligonucleotides encoding codon sets of an appropriate length can also be preferably used as a randomized variable region library. In this case, it is possible to replace CDR3 sequences alone, since sequence polymorphism is observed in the CDR3 of the heavy chain variable region. When diversifying the amino acid sequence of an antigen-binding molecule, it is preferable to generate variations in the amino acid residues at surface-exposed positions in the antigen-binding molecule. Surface-exposed position refers to a position where surface exposure and/or contact with an antigen is determined to be possible, based on the conformation, structural ensemble, and/or modeled structure of an antigen-binding molecule. In the variable region, such positions are generally the CDRs. Surface-exposed positions can be determined from the coordinates of a three dimensional model of the antigen-binding molecule using computer programs such as the InsightII program (Accelrys). Surface-exposed positions can also be determined using algorithms known in the art (for example, Lee and Richards (J. Mol. Biol. (1971) 55, 379-400); Connolly (J. Appl. Cryst. (1983) 16, 548-558)). Alternatively, the surface-exposed positions can be determined based on the information on the three dimensional structure obtained from antibodies and software suitable for protein modeling. Software that can be used for this purpose preferably includes the SYBYL Biopolymer Module software (Tripos Associates). When the algorithm requires the input size parameter from the user, the “size” of probe for use in computation is generally set to be about 1.4 Å or less in radius. Furthermore, a method for determining the surface-exposed region or area using PC software is described by Pacios (Comput. Chem. (1994) 18 (4), 377-386; and J. Mol. Model. (1995) 1, 46-53).

In still another embodiment, a naive library constructed from antibody genes derived from lymphocytes of healthy persons can also be particularly preferably used as a randomized variable region library (Gejima et al., (Human Antibodies (2002) 11, 121-129); and Cardoso et al., (Scand. J. Immunol. (2000) 51, 337-344)). Much variation is expected in the repertoire of antibody sequences derived from lymphocytes of healthy persons, because it is unbiased. In the present invention, an amino acid sequence containing a naive sequence refers to an amino acid sequence obtained from such a naive library.

In an embodiment of the present invention, antigen-binding domains of the present invention can be obtained from a library that contains a number of antigen-binding domains with sequences different from one another, which is constructed by combining a light chain variable region having a random sequence with a heavy chain variable region containing at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration. Without being particularly limited thereto, the libraries preferably include, for example, libraries of antigen-binding domains in which the heavy chain variable region of SEQ ID NO: 117 (6RL#9-IgG1) or SEQ ID NO: 119 (6KC4-1#85-IgG1) is combined with a light chain variable region having a random sequence. Alternatively, a light chain variable region having a germ-line sequence may be suitably selected and used instead of the light chain variable region having a random sequence. Without being particularly limited thereto, the libraries preferably include, for example, libraries of antigen-binding domains in which the heavy chain variable region of SEQ ID NO: 117 (6RL#9-IgG1) or SEQ ID NO: 119 (6KC4-1#85-IgG1) is combined with the light chain variable region having a germ-line sequence.

Furthermore, the above-described heavy chain variable region containing at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration can be designed in such a way that it additionally contains flexible residues. The flexible residues are not particularly limited in number and position, as long as the antigen-binding activity of antigen-binding domains of the present invention changes according to the calcium ion concentration. Specifically, the CDR sequences and/or FR sequences of the heavy chain and/or the light chain may contain one or more flexible residues. Without being particularly limited thereto, flexible residues that are introduced into the heavy chain variable region of SEQ ID NO: 117 (6RL#9-IgG1) include, for example, the entire amino acid residues of the heavy chain CDR1 and the heavy chain CDR2, and amino acid residues of the heavy chain CDR3 except for at positions 95, 96, and/or 100a. Meanwhile, flexible residues that are introduced into the heavy chain variable region of SEQ ID NO: 119 (6KC4-1#85-IgG1) include, for example, the entire amino acid residues of the heavy chain CDR1 and the heavy chain CDR2, and amino acid residues of the heavy chain CDR3 except for at positions 95 and/or 101.

Alternatively, a library that contains multiple antigen-binding domains with sequences different from one another can be constructed by combining a light chain variable region having a random sequence or a light chain variable region having a germ-line sequence with the above-described heavy chain variable region introduced with at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration. The libraries preferably include, for example, libraries of antigen-binding domains in which a light chain variable region having a random sequence or a light chain variable region having a germ-line sequence is combined with a heavy chain variable region in which specific amino acid residues in the heavy chain variable region are substituted with at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration. Without being particularly limited thereto, the amino acid residues include, for example, amino acid residues of the heavy chain CDR1, amino acid residues of the heavy chain CDR2, and the amino acids at positions 95, 96, 100a, and/or 101 in the heavy chain CDR3. As long as the amino acid residues form a calcium-binding motif and/or the antigen-binding activity changes according to the calcium ion concentration, the amino acid residues may be contained alone or in combination of two or more.

Even when the above-described heavy chain variable region which is introduced with at least one amino acid residue that changes the antigen-binding activity according to the calcium ion concentration is combined with a light chain variable region having a random sequence or a light chain variable region having a germ-line sequence, the heavy chain variable region can be designed in such a way that it also contains flexible residues. The flexible residues are not particularly limited in number and position, as long as the antigen-binding activity of antigen-binding domains of the present invention changes according to the calcium ion concentration. Specifically, the CDR sequences and/or FR sequences of the heavy chain may contain one or more flexible residues. Alternatively, amino acid sequences of the CDR1, CDR2, and/or CDR3 in the heavy chain variable region other than the amino acid residues that change the antigen-binding activity according to the calcium ion concentration may be randomized sequences, as in the above-described synthetic libraries. Without being particularly limited, when used as the light chain variable region, germ-line sequences preferably include, for example, those of SEQ ID NO: 58 (Vk1), SEQ ID NO: 59 (Vk2), SEQ ID NO: 60 (Vk3), and SEQ ID NO: 61 (Vk4).

In the present invention, known methods such as site-directed mutagenesis (Kunkel et al., (Proc. Natl. Acad. Sci. USA (1985) 82, 488-492)) and overlap extension PCR can be appropriately employed to modify amino acids. Furthermore, various known methods can also be used as a method for modifying amino acids into those other than natural amino acids (Annu. Rev. Biophys. Biomol. Struct. (2006) 35, 225-249; Proc. Natl. Acad. Sci. U.S.A. (2003) 100 (11), 6353-6357). For example, one may appropriately use a cell-free translation system (Clover Direct (Protein Express)) containing tRNAs linked with an unnatural amino acid on amber suppressor tRNAs, which are complementary to the UAG codon (amber codon) which is a stop codon.

KD values for antigen-binding domains of the present invention can be measured by methods known to those skilled in the art, for example, using Biacore (GE healthcare), Scatchard plot, or flow cytometer. Specifically, in the case of Biacore, antigen-binding molecules containing an antigen-binding domain of the present invention are immobilized on a chip and an antigen is passed as an analyte to determine KD. The measurement can be carried out under an acidic pH range condition and under a neutral pH range condition to calculate the value of KD (acidic pH)/KD (neutral pH). Meanwhile, the measurement can be carried out under a low calcium ion concentration condition and under a high calcium ion concentration condition to calculate the value of KD (low calcium ion concentration)/KD (high calcium ion concentration).

Antigen-binding domains of the present invention may exhibit, under different types of conditions at the same time, the property that the antigen-binding activity changes according to the ion concentration. For example, antigen-binding domains of the present invention may have the property that their antigen-binding activity is lower under an acidic pH range condition than under a neutral pH range condition, and is lower under a low calcium ion concentration condition than under a high calcium ion concentration condition.

Specifically, antigens of the present invention having two or more types of physiological activities include, for example:

activin, activin A, activin AB, activin B, activin C, activin RIA, activin RIA ALK-2, activin RIB ALK-4, activin RITA, activin RIIB, adiponectin, aFGF, AGE, allergen, amyloid β, amyloid immunoglobulin heavy chain variable region, amyloid immunoglobulin light chain variable region, anti-Id, antithrombin III, anthrax, apo A1, apo-serum amyloid A, apo-SAA, β-2-microglobulin, bFGF, B-lymphocyte stimulator (BLyS), BMP, BMP-2 (BMP-2a), BMP-3 (osteogenin), BMP-4 (BMP-2b), BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1), BMP-8 (BMP-8a). C10, C1 inhibitory factor, C1q, C3, C3a, C4, C5, C5a (complement 5a), cathepsin A, cathepsin B, cathepsin C/DPPI, cathepsin D, cathepsin E, cathepsin H, cathepsin L, cathepsin O, cathepsin S, cathepsin V, cathepsin X/Z/P, CCL, CCL1/I-309, CCL11/eotaxin, CCL12/MCP-5, CCL13/MCP-4, CCL14/HCC-1, CCL15/HCC-2, CCL16/HCC-4, CCL17/TARC, CCL18/PARC, CCL19/ELC, CCL2/MCP-1, CCL20/MIP-3-α, CCL21/SLC, CCL22/MDC, CCL23/MPIF-1, CCL24/eotaxin-2, CCL25/TECK, CCL26/eotaxin-3, CCL27/CTACK, CCL28/MEC, CCL3/M1P-1-α, CCL3L1/LD-78-β, CCL4/MIP-1-β, CCL5/RANTES, CCL6/C10, CCL7/MCP-3, CCL8/MCP-2, CCL9/10/MTP-1-γ, Clostridium botulinum toxin, Clostridium difficile toxin, Clostridium perfringens toxin, connective tissue growth factor (CTGF), CTLA-4, CX3CL1/fractalkine, CXCL, CXCL1/Gro-α, CXCL10, CXCL11/I-TAC, CXCL12/SDF-1-α/β, CXCL13/BCA-1, CXCL14/BRAK, CXCL15/lungkine, CXCL16, CXCL16, CXCL2/Gro-β CXCL3/Gro-γ, CXCL3, CXCL4/PF4, CXCL5/ENA-78, CXCL6/GCP-2, CXCL7/NAP-2, CXCL8/IL-8. CXCL9/Mig, CXCL10/IP-10, DC-SIGN, digoxin, EGF like domain containing protein 7, endotoxin, RSV F protein, F10, F11, F12, F13, F5, F9, factor Ia, factor IX, factor Xa, factor VII, factor VIII, factor VIIIc, FGF, FGF-19, FGF-2, FGF-2 receptor, FGF-3, FGF-8, fibronectin, GRO/MGSA, GRO-β, GRO-γ, Helicobacter pylori (H. pylori), hapten (NP-cap or NIP-cap), HB-EGF, HCMV gB envelope glycoprotein, Hep B gp120, Bacillus anthracis protective antigen, hepatitis C virus E2 glycoprotein, hepatitis E, hepcidin, herpes simplex virus (HSV) gB glycoprotein, HIV envelope proteins such as GP120, HIV MIB gp 120 V3 loop, HLA, HLA-DR, high mobility group box 1 (HMGB1), HSP47, Hsp90, HSV gD glycoprotein, human cytomegalovirus (HCMV), human serum albumin, human tissue plasminogen activator (t-PA), IFN-α, IFN-β, IFN-γ, IgE, IGF, immunoglobulin immune complex, immunoglobulin, influenza, inhibin, inhibin α, inhibin β, laminin 5, latency-associated peptide, latent TGF-1, latent TGF-1 bp1, LBP, LDL, leptin. Lewis-Y antigen, Lewis-Y-related antigen, LFA-1, LFA-3, lipoproteins, L-selectin, type 3 nonstructural protein of hepatitis C virus (NS3), oncostatin M, osteopontin, oxidized LDL, poly glycol chains of different size (for example, PEG-20, PEG-30, and PEG40), prekallikrein, prion protein, procalcitonin, proinsulin, prolactin, proprotein convertase PC9, prorelaxin, respiratory syncytial virus (RSV) F, rheumatoid factor. RSV Fgp, Sclerostin, serum amyloid P, serum albumin, Shiga like-toxin II, syndecan-1, tenascin, TGF, TGF-α, TGF-β, TGF-β Pan Specific, TGF-β1, TGF-β2, TGF-β3, TGF-β4, TGF-β5, TGF-1, thrombin, thrombopoietin (TPO), thyroxine binding globulin, TNF-α, TNF-β, TNIL-1, toxic metabolite, transforming growth factors (TGFs) such as TGF-α and TGF-β, VEGF, viral antigens, and von Willebrand factor (vWF). Particularly preferred examples include HMGB1, CTGF, and IgE. These antigens are preferably derived from mammals, particularly preferably from humans.

The gene and amino acid sequences of human HMGB1 have been deposited under GenBank accession number NM_002128 (SEQ ID NO: 22) and NP_002119 (SEQ ID NO: 23), respectively. In addition to human, the gene and amino acid sequences of mouse HMGB1 have been deposited under GenBank accession number NM_010439 (SEQ ID NO: 24) and NP_034569 (SEQ ID NO: 25), respectively; and the gene and amino acid sequences of rat HMGB1 have been deposited under GenBank accession number NM_012963 (SEQ ID NO: 26) and NP_037095 (SEQ ID NO: 27), respectively.

The gene and amino acid sequences of human CTGF have been deposited under GenBank accession number NM_001901 (SEQ ID NO: 28) and NP_001892 (SEQ ID NO: 29), respectively. In addition to human, the gene and amino acid sequences of mouse CTGF have been deposited under GenBank accession number NM_0 10217 (SEQ ID NO: 30) and NP_034347 (SEQ ID NO: 31), respectively; and the gene and amino acid sequences of rat CTGF have been deposited under GenBank accession number NM_022266 (SEQ ID NO: 32) and NP_071602 (SEQ ID NO: 33), respectively.

The gene sequences of the constant region of human IgE and mouse IgE have been deposited under GenBank accession number L00022 (SEQ ID NO: 34) and GenBank accession number X01857 (SEQ ID NO: 35), respectively.

Target molecules to which HMGB1 binds include receptor for advanced glycation endproducts (RAGE), Toll-like receptor 4 (TLR4), IL-1 receptor, Toll-like receptor 2 (TLR2), thrombospondin, triggering receptor expressed on myeloid cells-1 (TREM-1), and CD24. Meanwhile, reported substances that enhance the binding between HMGB1 and the above-described target molecules include DNA, RNA, lipopolysaccharide (LPS), interleukin-1β (IL-1β), chemokine (C-X-C motif) Ligand 12 (CXCL12), and nucleosomes. Preferred target molecules of the present invention include, for example, RAGE and TLR4.

Reported target molecules to which CTGF binds include insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), integrin αvβ3, transforming growth factor-β (TGF-β), bone morphogenetic protein-4 (BMP-4), LDL receptor-related protein-1 (LRP-1), vascular endothelial growth factor (VEGF), Wnt, heparan sulfate proteoglycans (HSPG), integrins, LDL receptor-related protein-5 (LRP-5), and LDL receptor-related protein-6 (LRP-6).

Reported target molecules to which IgE binds include FcεRI and FcεRII. These are also preferred examples of a target molecule of the present invention.

The present invention provides polynucleotides encoding antigen-binding molecules of the present invention. Polynucleotides are primarily constituted with DNA, RNA, other nucleotide analogs, and such.

The present invention provides vectors carrying polynucleotides of the present invention. Vectors for use in the present invention are not particularly limited in type, as long as they can stably carry inserted nucleic acids, and various vectors available in the market can be used. Gene cloning vectors include, for example, M13 vectors and pUC vectors. When vectors are used to produce antigen-binding molecules of the present invention, expression vectors are particularly useful. Expression vectors are not particularly limited, as long as they are capable of expressing polypeptides in vitro, in E. coli, in cultured cells, or in individual organisms. For example, vectors for in vitro expression include pBEST vectors (Promega); vectors for expression in E. coli include pGEX, pET, and pBluescript vectors (Stratagene); vectors for expression in cultured cells include pME18S-FL3 vector (GenBank Accession No. AB009864); vectors for expression in animal cells include pcDNA; and vectors for expression in individual organisms include pME18S vector (Mol Cell Biol. 8: 466-472 (1988)). Polynucleotides of the present invention can be inserted into vectors, for example, using the In-Fusion Advantage PCR Cloning Kit (Clontech).

The present invention provides host cells retaining vectors of the present invention. Host cells that can be used are not particularly limited, and for example, E. coli and various animal cells can be suitably used. Host cells can be used, for example, as a production system to produce or express antigen-binding molecules of the present invention. Such production systems include in vitro and in vivo production systems. The in vitro production systems include production systems using eukaryotic cells and those using prokaryotic cells.

Eukaryotic cells that can be used as host cells include, for example, animal cells, plant cells, and fungal cells. Animal cells include, for example, mammalian cells, for example, CHO (J. Exp. Med. (1995) 108: 94.0), COS, HEK293, 3T3, myeloma, BHK (baby hamster kidney), HeLa, and Vero; amphibian cells, for example, Xenopus oocytes (Valle et al., Nature (1981) 291: 338-340); and insect cells, for example, Sf9, Sf21, and Tn5. CHO-DG44, CHO-DX11B, COS7, HEK293, and BHK are preferably used. CHO is particularly preferable for large-scale expression. Vectors can be introduced into host cells, for example, by using techniques known to those skilled in the art, such as calcium phosphate methods, DEAE-dextran methods, methods using cationic liposome DOTAP (Boehringer-Mannheim), electroporation, lipofection, and microinjection. Alternatively, the Free Style 293 Expression System (Invitrogen) may be used to accomplish the process from gene introduction to polypeptide expression.

As plant cells, for example, cells derived from Nicotiana tabacum and Lemna minor are known as a protein production system. Calluses can be cultured from these cells to produce antigen-binding molecules of the present invention. Fungal cells known as a protein expression system include yeast cells, for example, cells of genus Saccharomyces such as Saccharomyces cerevisiae and Saccharomyces pombe; and cells of filamentous fungi, for example, cells of genus Aspergillus such as Aspergillus niger.

When prokaryotic cells are used, there are production systems that use bacterial cells. Bacterial cells known as a protein production system include, for example, Streptococcus, Staphylococcus, Escherichia coli, streptomyces, and Bacillus subtilis.

On the other hand, for example, production systems using animals or plants may be used as systems for producing polypeptides in vivo. A polynucleotide of interest is introduced into an animal or plant and the polypeptide is produced in the body of the animal or plant, and then collected. The hosts of the present invention include such animals and plants.

The production system using animals include those using mammals or insects. It is possible to use mammals such as goats, pigs, sheep, mice, and bovines (Vicki Glaser SPECTRUM Biotechnology Applications (1993)). The mammals may be transgenic animals. For example, a polynucleotide encoding an antigen-binding molecule provided by the present invention is prepared as a fusion gene with a gene encoding a polypeptide specifically produced in milk, such as the goat β casein. Next, goat embryos are injected with polynucleotide fragments containing the fusion gene, and then transplanted to female goats. Desired antigen-binding molecules can be obtained from milk produced by the transgenic goats, which are born from the goats that received the embryos, or their offspring. Hormones may be administered as appropriate to increase the volume of milk containing the antigen-binding molecule produced by the transgenic goats (Ebert et al., Bio/Technology (1994) 12: 699-702).

Insects such as silkworms may be used to produce the antigen-binding molecules provided by the present invention. When silkworms are used, baculoviruses carrying a polynucleotide encoding an antigen-binding molecule of interest can be used to infect silkworms, and the antigen-binding molecule of interest can be obtained from their body fluids.

Furthermore, when plants are used to produce the antigen-binding molecules provided by the present invention, for example, tobacco may be used. When tobacco is used, a polynucleotide encoding an antigen-binding molecule of interest is inserted into a plant expression vector, for example, pMON 530, and then the vector is introduced into bacteria, such as Agrobacterium tumefaciens. The bacteria are then allowed to infect tobacco such as Nicotiana tabacum, and the desired antigen-binding molecules can be collected from their leaves (Ma et al., Eur. J. Immunol. (1994) 24: 131-138). Alternatively, it is possible to infect duckweed (Lemna minor) with similar bacteria. After cloning, the desired antigen-binding molecules can be obtained from the duckweed cells (Cox K M et al., Nat. Biotechnol. 2006 December; 24(12): 1591-1597).

The thus obtained antigen-binding molecules may be isolated from the inside or outside (such as the medium and milk) of host cells, and purified as substantially pure and homogenous molecules. The methods for isolating and purifying antigen-binding molecules provided by the present invention are not particularly limited, and isolation and purification methods usually used for polypeptide purification can be used. Isolation and purification may be performed by appropriately selecting and combining, for example, column chromatographies, filtration, ultrafiltration, salting out, solvent precipitation, solvent extraction, distillation, immunoprecipitation, SDS-polyacrylamide gel electrophoresis, isoelectric focusing, dialysis, and recrystallization.

Chromatography includes, for example, affinity chromatography, ion exchange chromatography, hydrophobic chromatography, gel filtration chromatography, reverse-phase chromatography, and adsorption chromatography (Strategies for Protein Purification and Characterization: A Laboratory Course Manual. Ed Daniel R Marshak et al., (1996) Cold Spring Harbor Laboratory Press). Such chromatographic methods can be conducted using liquid phase chromatography such as HPLC and FPLC. Columns used for affinity chromatography include, protein A columns and protein G columns. Columns using protein A include, for example, Hyper D, POROS, and Sepharose F. F. (Pharmacia).

If needed, an antigen-binding molecule provided by the present invention can be modified arbitrarily, and peptides can be partially deleted by allowing an appropriate protein modification enzyme to act on the antigen-binding molecule. Such protein modification enzymes include, for example, trypsin, chymotrypsin, lysyl endopeptidases, protein kinases, and glucosidases.

The present invention also provides pharmaceutical compositions comprising an antigen-binding molecule of the present invention as an active ingredient. Pharmaceutical compositions can be used to treat diseases. It is preferable that pharmaceutical compositions of the present invention are used to treat diseases for which one of the causes is assumed to be an antigen that has physiological activity. The antigen is preferably an antigen having two or more types of physiological activities that can be reduced in vive by antigen-binding molecules of the present invention. In the present specification, “treatment” means to obtain pharmacological and/or physiological effects. Such an effect may be preventive in the sense that it completely or partially prevents the symptoms of a disease, or may be therapeutic in the sense that it completely or partially cures the symptoms of a disease. In the present specification, “treatment” includes all of the treatments for diseases in mammals, in particular humans. Furthermore, the “treatment” also includes preventing the onset of diseases in subjects who have not yet been diagnosed with a disease, restraining the progression of symptoms, and reducing the symptoms of diseases.

Pharmaceutical compositions of the present invention can be formulated by methods known to those skilled in the art (for example, Remington's Pharmaceutical Science, latest edition. Mark Publishing Company, Easton, USA). If needed, antigen-binding molecules of the present invention may be formulated in combination with other pharmaceutical ingredients. The pharmaceutical compositions may also comprise, for example, pharmaceutically acceptable carriers and additives. The pharmaceutical compositions of the present invention can also be used parenterally, for example, when they are formulated in a sterile solution or suspension for injection using water or any other pharmaceutically acceptable liquid. Dosage forms for oral and parenteral administration, and methods for producing them are well known to those skilled in the art, and may be produced according to conventional methods by mixing the pharmaceutical compositions of the present invention with pharmaceutically acceptable carriers and such. In the present invention, examples include sterile water, physiological saline, vegetable oils, emulsifiers, surfactants, excipients, vehicles, colorants, flavoring agents, preservatives, antiseptic agents, stabilizers, buffers, suspension agents, isotonizing agents, binders, disintegrating agents, lubricants, fluidity enhancing agents, flavor additives, and corrigents; however, the carriers are not limited to the above example, and other conventional carriers may be appropriately used. Specifically, light anhydrous silicic acid, lactose, crystalline cellulose, mannitol, starch, carmellose calcium, carmellose sodium, hydroxypropylcellulose, hydroxypropyl methylcellulose, polyvinyl acetal diethylaminoacetate, polyvinylpyrrolidone, gelatin, medium chain fatty acid triglyceride, polyoxyethylene hydrogenated castor oil 60, saccharose, carboxymethylcellulose, corn starch, and inorganic salts may be used. Pharmaceutical compositions of the present invention may be formulated by appropriately combining the above-described examples, and mixing them into unit dosage forms required for generally accepted drug manufacture. The amount of active ingredients in these preparations is determined to achieve an adequate dose within the indicated range.

Pharmaceutical compositions of the present invention can be administered orally or parenterally; however, parenteral administration is preferred, which specifically includes injection, transnasal administration, transpulmonary administration, and transdermal administration. Injection includes, for example, intravenous administration, intramuscular administration, intraperitoneal administration, and subcutaneous administration. The dose can be suitably selected from the range of 0.0001 mg to 1000 mg/kg body weight of a patient or within the range of 0.001 mg to 10000 mg/patient; however, the dose is not limited to this example. Subjects to be administered are mammals, preferably humans.

The present invention also provides kits comprising an antigen-binding molecule of the present invention or a pharmaceutical composition of the present invention, and kits for use in various methods of the present invention. The kits of the present invention may additionally contain in a package instruction manuals describing how to use them, as necessary. In addition, the kits of the present invention can be preferably used in: (i) methods for reducing antigen concentration in plasma; (ii) methods for enhancing antigen incorporation into cells; or (iii) methods for reducing the physiological activity of antigens in vivo.

In the present invention, preferred antigens include, for example, HMGB1. Diseases for which one of the causes is assumed to be HMGB1 include sepsis, trauma, acute respiratory distress syndrome (ARDS), ischemia-reperfusion injury in the brain, heart, liver, kidney, and such, pancreatitis, nephritis, hepatitis, colitis, meningitis, endophthalmitis, myopathy, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), diabetes, multiple sclerosis (MS), colorectal cancer, osteosarcoma, cervical cancer, liver cancer, lymphoma, nasopharyngeal cancer, prostate cancer, skin cancer, urothelial cancer, lung cancer, autism, seizure, sleep apnea syndrome, HIV infection, pulmonary fibrosis, and burn injury. Other preferred antigens include, for example, CTGF. Diseases for which one of the causes is assumed to be CTGF include fibrosis such as pulmonary fibrosis and hepatic fibrosis. Other preferred antigens include, for example, IgE. Diseases for which one of the causes is assumed to be IgE include allergic diseases such as bronchial asthma, atopic dermatitis, and pollinosis.

The present invention also provides methods for producing antigen-binding molecules of the present invention, which comprise the steps of:

-   -   (a) selecting an antigen having two or more types of         physiological activities;     -   (b) obtaining an antigen-binding domain;     -   (c) obtaining at least one receptor-binding domain;     -   (d) selecting from antigen-binding domains obtained in step (b)         a domain of which antigen-binding activity changes according to         the ion concentration;     -   (e) selecting from receptor-binding domains obtained in step (c)         a domain that has human FcRn-binding activity under an acidic pH         range condition and of which human Fc receptor-binding activity         under a neutral pH range condition is greater than the human Fc         receptor-binding activity of native human IgG;     -   (f) producing an antigen-binding molecule in which the         antigen-binding domain selected in step (d) is linked to the         receptor-binding domain selected in step (e); and     -   (g) selecting from antigen-binding molecules produced in         step (f) an antigen-binding molecule which inhibits one or more         types of the physiological activities of the antigen by binding         to the antigen while allowing for the antigen to retain at least         one type of physiological activity.

Antigen-binding domains of the present invention may be prepared by any methods. For example, when an antigen-binding domain is an antibody or a fragment thereof (such as a variable region, Fab, F(ab′)2, Fv, or CDR), it can be prepared by antibody library methods, hybridoma methods, B cell cloning methods (Bemasconi et al., Science (2002) 298, 2199-2202; or WO2008/081008), and such. Meanwhile, antibodies and fragments thereof prepared as described above may be modified at at least one amino acid.

There are a number of known methods for constructing antibody libraries. Regarding phage display libraries, for example, those skilled in the art can prepare them by referring to documents such as Clackson et al., Nature 1991, 352: 624-8; Marks et al., J. Mol. Biol. 1991, 222: 581-97; Waterhouses et al., Nucleic Acids Res. 1993, 21: 2265-6; Griffiths et al., EMBO J. 1994, 13: 324.0-60; Vaughan et al., Nature Biotechnology 1996, 14: 309-14; Kang A S et al., Proc Natl Acad Sci USA (1991) 88, 4363-4366; and Japanese Patent Kohyo Publication No. (JP-A) H10-504970 (unexamined Japanese national phase publication corresponding to a non-Japanese international publication). When the variable regions of antibodies in a phage display library are expressed as single-chain antibodies (scFv) on the surface of phages, phages that bind to antigens can be selected by panning. The genes of selected phages are analyzed to determine the DNA sequences encoding the variable regions of antibodies that bind to the antigens. Once the DNA sequences of the variable regions of antibodies are revealed, they can be linked to the DNAs encoding desired constant regions and inserted into appropriate expression vectors. The resulting vectors are introduced into host cells for expression to produce the antibodies as recombinant proteins. These methods are already well known, and one can refer to the following documents: WO92/01047, WO92/20791, WO93/06213, WO93/11236, WO93/19172, WO95/01438, and WO95/15388. In addition to phage display libraries, it is possible to use known antibody libraries such as ribosome display libraries (Schaffitzel C et al., J. Immunol. Methods (1999) 231, 119-135.), cell display libraries (Fuchs P et al., Biotechnology (1991) 9, 1369-1372; Boder E T & Wittrup K D, Nat Biotechnol (1997) 15, 553-557; WO95/15393), nucleotide display libraries (Cull M G et al., Proc Nalt Acad Sci USA (1992) 89, 1865-1869; Roberts R D & Szostak J W, Proc Natl Acad Sci USA (1997) 94, 12297-12302), and eukaryotic virus display libraries (Grabherr R & Ernst W. Comb Chem High Throughput Screen (1991) 4, 185-192).

As a hybridoma method for preparing antibodies, basically known techniques are used. A desired antigen or cells expressing the desired antigen are used as a sensitizing antigen. Immune cells obtained by immunization with the antigen according to a conventional immunization method are fused with known parental cells by a conventional cell fusion method. The resulting cells are screened for cells producing monoclonal antibodies (hybridomas) by a conventional screening method. Furthermore, by using reverse transcriptase, cDNAs encoding the variable regions of the antibodies can be prepared from the mRNA of the obtained hybridomas. The cDNAs are linked to the DNA encoding a desired constant region and inserted into an appropriate expression vector. The resulting vectors are introduced and expressed in host cells to produce the antibodies as recombinant proteins.

More specifically, the sensitizing antigens include, but are not limited to, for example, both complete antigens with immunogenicity, and incomplete antigens without immunogenicity including haptens. For example, the full-length proteins of interest and partial peptides can be used. In addition, it is known that substances composed of polysaccharides, nucleic acids, lipids, and such can serve as an antigen, and are not particularly limited. Antigens can be prepared by methods known to those skilled in the art, for example, according to methods using baculoviruses (for example, WO98/46777). Hybridomas can be produced, for example, according to the method of Milstein et al. (G. Kohler and C. Milstein, Methods Enzymol. 1981, 73: 3-46). When the immunogenicity of an antigen is low, it can be linked to a macromolecule having immunogenicity, such as albumin, and then used for immunization. Alternatively, the antigen may be linked to other molecules, if necessary.

Hybridomas can be obtained by immunizing animals using suitable sensitizing antigens described above. Alternatively, antibody-producing cells can be prepared by in vitro immortalization of lymphocytes capable of producing antibodies. Various mammals can be used for immunization, and such animals generally used include rodents, lagomorphas and primates. Such animals include, for example, rodents such as mice, rats, and hamsters; lagomorphas such as rabbits; and primates such as monkeys including cynomolgus monkeys, rhesus monkeys, hamadryas baboons, and chimpanzees. In addition, transgenic animals with the repertoire of human antibody genes are also known, and such animals can be immunized with a desired antigen to obtain human antibodies (see WO93/12227; WO92/03918; WO94/02602; WO96/34096; WO96/33735; Mendez et al., Nat. Genet. 1997, 15: 146-56). Instead of using such transgenic animals, for example, human lymphocytes can be sensitized in vitro with a desired antigen, and the sensitized lymphocytes can be fused with human myeloma cells, for example, U266 to obtain desired human antibodies with antigen-binding activity (see Japanese Patent Kohyo Publication No. (JP-A) H01-59878 (unexamined Japanese national phase publication corresponding to a non-Japanese international publication)).

Animals are immunized, for example, by appropriately diluting and suspending a sensitizing antigen in phosphate-buffered saline (PBS), physiological saline, or such, and after combining it with an adjuvant and emulsifying if needed, injecting it intraperitoneally or subcutaneously to the animals. Then, the sensitizing antigen combined with Freund's incomplete adjuvant is preferably administered several times every four to 21 days. Antibody production can be confirmed by measuring the titer of antibody of interest in the sera of the animals according to conventional methods.

To produce hybridomas, antibody-producing cells such as lymphocytes obtained from animals immunized with a desired antigen are fused with myeloma cells using conventional fusion agents (for example, polyethylene glycol) (Goding, Monoclonal Antibodies: Principles and Practice, Academic Press, 1986, 59-103). If needed, hybridomas can be cultured and grown, and the binding specificity of antibodies produced by the hybridomas can be measured using known analysis methods, such as immunoprecipitation, radioimmunoassay (RIA), and enzyme-linked immunosorbent assay (ELISA). Then, as necessary, hybridomas producing the antibodies of interest with determined specificity, affinity, or activity can be subcloned by methods such as limiting dilution.

Next, genes encoding antibodies can be cloned from hybridomas or antibody-producing cells (such as sensitized lymphocytes) using probes capable of specifically binding to antibody genes (for example, oligonucleotides complementary to sequences encoding the antibody constant regions). Alternatively, the genes can be cloned from mRNA by RT-PCR. Immunoglobulins are classified into five different classes: IgA, IgD, IgE, IgG, and IgM. These classes are further divided into several subclasses (isotypes) (for example, IgG1, IgG2, IgG3, and IgG4).

Receptor-binding domains of the present invention may be obtained by any methods. For example, when a receptor-binding domain is an anti-FcRn antibody or a fragment thereof (a variable region, Fab, F(ab′)2, Fv, CDR, etc.), it can be prepared by the above-described antibody library methods and hybridoma methods. Other examples of receptor-binding domains include the Fc region of an antibody (IgG) and regions containing the Fc region (antibody constant regions and full length antibodies). When a receptor-binding domain is the Fc region of an IgG, it may be modified at at least one amino acid.

Arbitrary amino acids can be added, deleted, and/or substituted in polypeptides by methods known to those skilled in the art, for example, site-directed mutagenesis (Hashimoto-Gotoh T. et al., Gene (1995) 152, 271-275; Zoller M. J. & Smith M., Methods Enzymol (1983) 100, 468-500; Kramer W. et al., Nucleic Acids Res (1987) 12, 9441-9456; Kramer W. & Fritz H. J., Methods Enzymol (1987) 154, 350-367; Kunkel T. A., Proc Natl Acad Sci USA (1985) 82, 488-492).

Methods for producing chimeric antibodies are known, and in the case of a human-mouse chimeric antibody, for example, DNA encoding the variable region of a mouse antibody can be linked to a DNA encoding the constant region of a human antibody and inserted into an expression vector, and then introducing the vector into a host to produce the chimeric antibody.

Humanized antibodies are also referred to as “reshaped human antibodies”, and result from grafting the complementarity determining region (CDR) of an antibody derived from a nonhuman mammal, for example, a mouse, into a human antibody at its CDR. Methods for identifying CDRs are known (Kabat et al., Sequence of Proteins of Immunological Interest (1987) National Institute of Health, Bethesda, Md.; Chothia et al., Nature (1989) 342: 877). General genetic recombination techniques for grafting CDRs are also known (see European Patent Application Publication No. EP 125023; WO96/02576). Humanized antibodies can be produced by known methods, for example, with a system using common expression vectors, by determining the CDR of a mouse antibody and preparing a DNA encoding an antibody in which the CDR is linked to the framework region (FR) of a human antibody. Such DNAs can be synthesized by assemble PCR, using as primers several oligonucleotides designed to include overlapping portions at the ends of both the CDR and FR regions (see the method described in WO98/13388). Human antibody FRs linked via CDRs are selected such that the CDRs form a suitable antigen binding site. If required, amino acids in the FRs of an antibody variable region may be altered in such a way that the CDRs of the reshaped human antibody form a suitable antigen binding site (Sato et al., Cancer Res. (1993) 53: 10.01-6). Amino acid residues that can be altered in the FRs include portions that directly bind to an antigen via non-covalent bonds (Amit et al., Science (1986) 233: 747-53), portions that influence or act on the CDR structure (Chothia et al., J. Mol. Biol. (1987) 196: 901-17), and portions involved in the interaction between VH and VL (EP 239400).

In addition to the humanization techniques described above, antibodies may be modified to improve their biological properties, for example, antigen affinity. In the present invention, alteration can be achieved using methods such as site-directed mutagenesis (see, for example, Kunkel (1910.0) Proc. Natl. Acad. Sci. USA 82: 488), PCR mutagenesis, and cassette mutagenesis. In general, mutant antibodies with improved biological properties show amino acid sequence homology and/or similarity of 70% or higher, more preferably 80% or higher, and even more preferably 90% or higher (for example, 95% or higher, 96%, 97%, 98%, 99%, etc.), to the amino acid sequence of the original antibody variable region. In the present specification, sequence homology and/or similarity is defined as the ratio of amino acid residues that are homologous (same residue) and/or similar (residues classified into the same group based on the general properties of amino acid side chains) to the amino acid residues of the original sequence, after the sequence homology value has been maximized by sequence alignment and gap introduction, as necessary. In general, native amino acid residues are classified based on the characteristics of their side chains into the following groups:

-   -   (1) hydrophobic: alanine, isoleucine, valine, methionine, and         leucine;     -   (2) neutral, hydrophilic: asparagine, glutamine, cysteine,         threonine, and serine;     -   (3) acidic: aspartic acid and glutamic acid;     -   (4) basic: arginine, histidine, and lysine;     -   (5) residues that have influence on chain configuration: glycine         and proline; and     -   (6) aromatic: tyrosine, tryptophan, and phenylalanine.

In methods for producing antigen-binding molecules of the present invention, a number of antigen-binding domains are prepared, and domains of which antigen-binding activity changes according to the ion concentration can be selected from among them; or a number of domains are prepared by modifying an arbitrary antigen-binding domain by adding, deleting, and/or substituting at least one amino acid, and domains of which antigen-binding activity changes according to the ion concentration can be selected from among them. Alternatively, antigen-binding domains that inhibit one or more of the physiological activities of an antigen by binding to the antigen but allow for the antigen to retain at least one type of physiological activity may be appropriately selected from a number of antigen-binding domains.

In methods for producing antigen-binding molecules of the present invention, whether the binding of the antigen-binding molecule or the antigen-binding domain thereof to an antigen inhibits one or more types of the physiological activities of the antigen or allows for the antigen to retain at least one type of physiological activity can also be confirmed, by measuring whether one or more of the activities of the antigen to bind target molecules are inhibited or whether the activity to bind at least one type of target molecule is retained.

In methods for producing antigen-binding molecules of the present invention, a number of receptor-binding domains are prepared, and from among them, domains that have human FcRn-binding activity under an acidic pH range condition, and of which human Fc receptor-binding activity under a neutral pH range condition is greater than that of native human IgG can be selected; or a number of domains are prepared by modifying an arbitrary receptor-binding domain by adding, deleting, and/or substituting at least one amino acid, and from among them, domains that have human FcRn-binding activity under an acidic pH range condition, and of which human Fc receptor-binding activity under a neutral pH range condition is greater than that of native human IgG can be selected.

In methods for producing antigen-binding molecules of the present invention, in order to produce an antigen-binding molecule in which an antigen-binding domain is linked to a receptor-binding domain, polynucleotides encoding the antigen-binding domain and the receptor-binding domain are constructed, linked together in frame, inserted into an expression vector, and expressed in host cells. The antigen-binding domain may be linked directly to the receptor-binding domain, or indirectly using an arbitrary peptide linker that can be introduced by genetic engineering or using a synthetic compound linker (for example, the linkers disclosed in Protein Engineering (1996) 9, 299-305). Such peptide linkers are not particularly limited in length and amino acid sequence; however, peptides of 100 amino acids or less, preferably 50 amino acids or less, more preferably 30 amino acids or less, and particularly preferably 10 amino acids or less are generally used.

The present invention also provides methods of screening for antibodies of which antigen-binding activity changes depending on conditions, which comprise the steps of:

-   -   (a) preparing antibody-producing cells;     -   (b) contacting an antigen with the cells of (a) under the first         condition;     -   (c) selecting from the cells of step (b), cells bound to a         specific amount of antigen or more;     -   (d) exposing the cells of step (c) to the second condition; and     -   (e) selecting from the cells of step (d), cells in which the         amount of antigen binding has been reduced as compared to step         (c).

More preferred embodiments of the above-described method include methods comprising the steps of:

-   -   (a) preparing antibody-producing cells;     -   (b) contacting an antigen with the cells of (a) under the first         condition;     -   (c) contacting an anti-IgG antibody with the cells of step (b);     -   (d) selecting from the cells of step (c), cells bound to a         specific amount of antigen or more and bound to a specific         amount of anti-IgG antibody or more;     -   (e) exposing the cells of step (d) to the second condition; and     -   (f) selecting from the cells of step (e), cells in which the         amount of antigen binding has been reduced as compared to step         (d).

Sill more preferred embodiments of the above-described method include methods comprising the steps of:

-   -   (a) preparing antibody-producing cells;     -   (b) contacting an antigen with the cell of (a) under the first         condition;     -   (c) enriching cells bound to the antigen among the cells of step         (b);     -   (d) contacting an anti-IgG antibody with the cells of step (c);     -   (e) selecting from the cells of step (d), cells bound to a         specific amount of antigen or more and bound to a specific         amount of anti-IgG antibody or more;     -   (f) exposing the cells of step (e) to the second condition; and     -   (g) selecting from the cells of step (f), cells in which the         amount of antigen binding has been reduced as compared to step         (e).

In the present invention, “antibody-producing cells” are not particularly limited as long as they contain an antibody gene and express the antibody protein; however, they are preferably naturally-occurring cells producing antibodies within an animal body, more preferably lymphocytes, and still more preferably B cells. Animals can be appropriately selected from various mammals (such as mice, rats, hamsters, rabbits, cynomolgus monkeys, rhesus monkeys, hamadryas baboons, chimpanzees, and humans); however, rabbits are particularly preferable in the present invention. It is also preferable to use animals immunized with desired antigens. Antibody-producing cells may be naturally-occurring cells or artificially produced cells such as hybridomas and genetically modified cells. Antibody-producing cells for use in the present invention preferably have the property that they secrete antibodies to the outside of the cells (secretory antibodies) and/or the property that they present antibodies on the cell membrane (membrane-bound antibodies). Naturally occurring antibody-producing cells in the animal body can be preferably collected, for example, from spleen, lymph nodes, and blood (peripheral blood mononuclear cells). Such methods are known to those skilled in the art, and are also described in the Examples below.

In the present invention, “the first condition” and “the second condition” mean two types of different conditions and arbitrary conditions can be set when one desires to obtain an antibody of which antigen-binding activity varies between the conditions. Preferred examples in the present invention include extracellular condition and intracellular condition. The category of conditions is not particularly limited as long as antibody-producing cells are exposed to the conditions, and examples include temperature, pH, compositions in media, and the concentrations thereof. The conditions preferably include ion concentration, particularly preferably hydrogen ion concentration (pH) and calcium ion concentration. The intracellular condition preferably refers to a condition characteristic of the internal environment of an endosome, and the extracellular condition preferably refers to a condition characteristic of the environment in plasma.

The extracellular pH is neutral as compared to that inside the cell, and conversely the intracellular pH is acidic as compared to that outside the cell. A neutral pH range preferred in the present invention is pH 6.7 to pH 10.0, more preferably pH 7.0 to pH 9.0, still more preferably any of pH 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0, and particularly preferably pH 7.4 which is close to the pH in plasma (in blood). Meanwhile, an acidic pH range preferred in the present invention is pH 4.0 to pH 6.5, more preferably pH 5.0 to pH 6.5, still more preferably any of pH 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, and 6.5, and particularly preferably pH 5.8 to pH 6.0 which is close to the pH in the early endosome in vivo.

Meanwhile, the extracellular calcium ion concentration is higher than that inside the cell, and conversely the intracellular calcium ion concentration is lower than that outside the cell. A high calcium ion concentration preferred in the present invention is 100 μM to 10 mM, more preferably 200 μM to 5 mM, and particularly preferably 0.5 mM to 2.5 mM which is close to the calcium ion concentration in plasma (in blood). Meanwhile, a low calcium ion concentration preferred in the present invention is 0.1 μM to 30 μM, more preferably 0.5 μM to 10 μM, and particularly preferably 1 μM to 5 μM which is close to the calcium ion concentration in the early endosome in vivo. Low calcium ion concentration can also be achieved by adding a chelating agent such as EDTA, instead of reducing the amount of calcium added.

“The first condition” and “the second condition” may include several conditions at the same time. For example, “the first condition” may be a neutral pH condition and a high calcium ion concentration condition, and “the second condition” may be an acidic pH condition and a low calcium ion concentration condition.

Antigens may be any substances as long as it is possible to produce antibodies against them. The type of antigen is not particularly limited, and it preferably comprises polypeptides. Meanwhile, in the above-described antibody screening methods of the present invention, antigens are preferably labeled with certain substances that can be detected with high sensitivity. The labeling substances may be linked directly to antigens, or indirectly to antigens using antigen-antibody reaction or biotin-avidin reaction. The labeling substances include, for example, radioisotopes, chemiluminescent compounds, fluorescent compounds, phosphorescent compounds, magnetic particles, and enzymes, particularly preferably fluorescent compounds. Fluorescent compounds include, for example, fluorescein isothiocyanate (FITC), phycoerythrin (PE), PE-Cyanin5 (PE-Cy5), PE-Cyanin5.5 (PE-Cy5.5), PE-Cyanin7 (PE-Cy5), rhodamine isothiocyanate. Texas Red, PE-Texas Red-x (ECD), allophycocyanin (APC), APC-Cyanin 7 (APC-Cy7, PharRed), Peridinin Chlorophyll Protein (Per-CP), and Per-CP-Cyanin5.5 (PerCP-Cy5.5).

Furthermore, in the above-described antibody screening methods of the present invention, anti-IgG antibodies are also preferably labeled with certain substances that can be detected with high sensitivity. Cells to which anti-IgG antibodies are bound can be selected from antibody-producing cells to increase the percentage of cells expressing IgG subclasses. The presence of IgG expression in B cells namely suggests that class switching to IgG is taking place. To enrich cells producing such matured antibodies is expected to be beneficial from the viewpoint of screening for antibodies with strong binding activity. The labeling substances may be linked directly to antigens, or indirectly to antigens using antigen-antibody reaction or biotin-avidin reaction. The labeling substances include, for example, those described above. When an antigen and an anti-IgG antibody are both used, it is desirable that the labeling substances for them are different from each other and their detection methods are different (each can be detected independently). Antigens and anti-IgG antibodies can be labeled by referring to methods known to those skilled in the art (for example, U.S. Pat. No. 5,057,313 and U.S. Pat. No. 5,156,840).

In the above-described antibody screening methods provided by the present invention, the step of selecting cells bound to a specific amount of antigen or more and/or a specific amount of anti-IgG antibody or more is preferably achieved by detecting the above-described labeling substances. For example, when an antigen and/or an anti-IgG antibody are each labeled with a different type of fluorescent compound, whether a specific amount of antigen or more and/or a specific amount of anti-IgG antibody or more is bound to cells can be assessed by testing whether the fluorescence emitted from each fluorescent compound is detected to be at a specific lever or higher. The specific level can be set arbitrarily by those skilled in the art depending on the purpose. In the present invention, it is preferable that the selection step is achieved using FACS (Fluorescence Activated Cell Sorting).

In the above-described antibody screening methods provided by the present invention, it is preferable that the step of enriching antigen-bound cells is achieved by detecting the above-described labeling substances. For example, when an antigen is labeled with magnetic particles, antigen-bound cells can be separated from cells not bound by the antigen using magnetic devices. Antigen-bound cells can be enriched by removing cells not bound by the antigen. In the present invention, it is preferable that the enriching step is achieved by using the MACS (Magnetic Activated Cell Sorting (Registered Trademark)).

By using the above-described antibody screening methods provided by the present invention, a large amount of antibody-producing cells can be simply and efficiently screened for antibodies with antigen-binding activity that changes according to condition. As compared to conventional methods, the methods enable one to drastically increase the number of cells that can be screened, and thus greatly raise the probability to find rare antibodies that have been previously undetectable. Thus, the above-described antibody screening methods of the present invention are useful.

The present invention also provides methods for reducing antigen concentration in plasma by administering an antigen-binding molecule of the present invention, methods for enhancing antigen incorporation into cells by administering an antigen-binding molecule of the present invention, and methods for reducing the physiological activity of antigens in vivo by administering an antigen-binding molecule of the present invention.

The present invention also provides therapeutic agents for diseases, which comprise an antigen-binding molecule of the present invention as an active ingredient. The diseases include, for example, diseases for which one of the causes is assumed to be HMGB1, diseases for which one of the causes is assumed to be CTGF, and diseases for which one of the causes is assumed to be IgE.

The present invention also provides kits comprising antigen-binding molecules of the present invention for use in methods for reducing antigen concentration in plasma, methods for enhancing antigen incorporation into cells, and methods for reducing the physiological activity of antigens in vivo.

The present invention also provides methods for treating diseases for which one of the causes is assumed to be an antigen that has physiological activity, methods for reducing antigen concentration in plasma, methods for enhancing antigen incorporation into cells, and methods for reducing the physiological activity of antigens in vivo, which comprise the step of administering antigen-binding molecules of the present invention.

The present invention also provides agents for treating diseases for which one of the causes is assumed to be an antigen that has physiological activity, agents for reducing antigen concentration in plasma, agents for enhancing antigen incorporation into cells, and agents for reducing the physiological activity of antigens in vivo, which comprise an antigen-binding molecule of the present invention as an active ingredient.

The present invention also provides antigen-binding molecules of the present invention for use in methods for treating diseases for which one of the causes is assumed to be an antigen that has physiological activity, methods for reducing antigen concentration in plasma, methods for enhancing antigen incorporation into cells, and methods for reducing the physiological activity of antigens in vivo.

The present invention also provides the use of antigen-binding molecules of the present invention in the production of agents for treating diseases for which one of the causes is assumed to be an antigen that has physiological activity, agents for reducing antigen concentration in plasma, agents for enhancing antigen incorporation into cells, and agents for reducing the physiological activity of antigens in vivo.

The present invention also provides processes for producing agents for treating diseases for which one of the causes is assumed to be an antigen that has physiological activity, agents for reducing antigen concentration in plasma, agents for enhancing antigen incorporation into cells, and agents for reducing the physiological activity of antigens in vivo, which comprise the step of using an antigen-binding molecule of the present invention. Such diseases include, for example, diseases for which one of the causes is assumed to be HMGB1, diseases for which one of the causes is assumed to be CTGF, and diseases for which one of the causes is assumed to be IgE.

Amino acids contained in the amino acid sequences of the present invention may be post-translationally modified (for example, the modification of an N-terminal glutamine into a pyroglutamic acid by pyroglutamylation is well-known to those skilled in the art). Naturally, such post-translationally modified amino acids are included in the amino acid sequences in the present invention.

All prior art documents cited in the specification are incorporated herein by reference.

EXAMPLES

Herein below, the present invention will be specifically described with reference to the Examples, but it is not to be construed as being limited thereto.

Example 1 Construction of Anti-HMGB1 Antibodies by the Rabbit B Cell Cloning Method Preparation of HMGB1

HMGB1 was prepared as an antigen by the following procedure. An animal cell expression vector inserted with a DNA sequence encoding human HMGB1 (GenBank accession number NP002119, SEQ ID NO: 7) was constructed and used in combination with FreeStyle293 (Invitrogen) to express the full-length human HMGB1 protein in the culture supernatant. From the resulting culture supernatant, the HMGB1 protein was purified by cation-exchange column chromatography, anion-exchange chromatography, and gel filtration chromatography.

Immunization of Animals with the Antigen

Rabbits were immunized with HMGB1. The initial immunization was carried out by intracutaneously injecting 100 μg of the HMGB1 protein included in complete Freund's adjuvant (CFA). Then, booster immunization was performed with the HMGB1 protein included in incomplete Freund's adjuvant (IFA) at 50 μg each time, twice or more times at intervals of one week or more. Antibody titers were determined to confirm antibody production in the animal bodies.

Tissue Sampling from Immunized Animals and Preparation of Single-Cell Suspensions

Animals which had been confirmed to produce antibodies were euthanized to collect their spleens, lymph nodes, and blood. Peripheral blood mononuclear cells (PBMCs) were prepared from the blood. An equal volume of the blood was carefully overlaid onto Histpaque-1077 (Sigma) in a 50-ml centrifuge tube, and centrifuged at 400×g and 25° C. for 30 minutes. After centrifugation, the PBMC layer was carefully collected with a glass Pasteur pipette and transferred into a sterile 50-ml tube. About 10 volumes of RPMI-1640 containing 2% FBS was added to the collected cell suspension. The cells were washed by centrifugation at 1000×g for 5 minutes followed by removing the supernatant. The same washing treatment was carried out again to prepare PBMCs. The PBMCs were stained with trypan blue, and the cell density was determined with a hemocytometer.

The collected spleens and lymph nodes were filtered through 70-μm Cell Strainers (BD Falcon) using the plunger of a 5-ml syringe to prepare single-cell suspensions. The cells were collected into sterile 50-ml tubes using RPMI medium containing 2% FBS. The cells were washed by centrifugation at 1000×g for 5 minutes followed by removing the supernatant. 50 ml of RPMI-1640 containing 2% FBS was added, and the cells were washed again. After the final washing, the cells were stained with trypan blue, and the cell density was determined with a hemocytometer.

Collection of Antigen-Binding B Cells

The single-cell suspensions from the blood, spleens, and lymph nodes prepared by the above method were centrifuged at 1000×g for 5 minutes twice to wash the cells with HBSS (20 mM HEPES, 5.3 mM KCl, 0.4 mM KH₂PO₄, 4.2 mM NaHCO₃, 0.3 mM Na₂HPO₄, 0.1% BSA, 2 mM CaCl₂, 5 mM glucose, 138 mM NaCl, pH 7.4). A solution with biotinylated human HMGB1 diluted to 500 nM with HBSS was prepared and added to the cells so that the density is 1E08 cells/100 μl or less, and the cells were suspended. Biotinylated HMGB1 was prepared by labeling the HMGB1 protein using EZ-Link NHS-PEG4-Biotin and Biotinylation Kit (Thermo Scientific) according to the attached protocol, and then dialyzing against TBS/300 mM NaCl (10 mM Tris-HCl/300 mM NaCl) using a Microdialyzer (TOMY). The cell suspensions were incubated on ice for 30 minutes. Then, the cells were washed with 50 ml of HBSS to remove biotinylated HMGB1 that was not bound to the cells. A solution of MACS (Registered Trademark) streptavidin beads (Miltenyi Biotech) diluted 10 times with HBSS was prepared and added to the cells so that the density was 1E08 cells/500 μl or less to suspend them. The cell suspensions were incubated on ice for 30 minutes. After washing with 50 ml of HBSS, the cells were combined with HBSS so that the density was 1E08 cells/500 μl or less, and suspended. From the cell suspensions, fractions of positive cells to which MACS streptavidin beads were bound were collected using the autoMACS Pro Separator.

A solution of biotinylated HMGB1 diluted with HBSS was prepared again, and added to the collected cells so that the density was 1E08 cells/100 μl or less, and the cells were suspended. After incubating the cell suspensions on ice for 30 minutes, the cells were washed with 50 ml of HBSS. This secondary incubation with biotinylated human HMGB1 was omitted in some cases. Solutions of streptavidin-FITC (BD) and mouse anti-rabbit IgG-PE (Southern Biotech) diluted with HBSS were prepared and added to the cells so that the density was 1E08 cells/100 μl or less, and the cells were suspended. After incubating the cell suspensions on ice for 30 minutes, the cells were washed with 50 ml of HBSS. Next, HBSS was added to the cells so that the density was 1E07 cells/100 μl or less and they were suspended. The cell fractions whose FITC and PE fluorescence intensities were both high were collected from the cell suspensions using FACSAria (BD).

Collection of B Cells that Express Antigen-Binding Antibodies Whose Dissociation Ability is Altered Depending on the Change in pH or Ca²⁺ Ion Concentration

B cells that express antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration were enriched and collected by the following method. The prepared single-cell suspensions from blood, spleens, and lymph nodes were centrifuged at 1000×g for 5 minutes twice to wash the cells with HBSS (20 mM HEPES, 5.3 mM KCl, 0.4 mM KH₂PO₄, 4.2 mM NaHCO₃, 0.3 mM Na₂HPO₄, 0.1% BSA, 2 mM CaCl₂, 5 mM glucose, 138 mM NaCl, pH 7.4). A solution of biotinylated HMGB1 diluted to 500 nM with HBSS was prepared and added to the cells so that the density was 1E08 cells/100 μl or less, and the cells were suspended. After incubating the cell suspensions on ice for 30 minutes, the cells were washed with 50 ml of HBSS to remove biotinylated HMGB1 that was not bound to the cells. A solution of MACS streptavidin beads (Miltenyi Biotech) diluted 10 times with HBSS was prepared and added to the cells so that the density was 1E08 cells/500 μl or less, and the cells were suspended. The cell suspensions were incubated on ice for 30 minutes. After washing with 50 ml of HBSS, HBSS was added to the cells so that the density was 1E08 cells/500 μl or less, and the cells were suspended. Positive fractions of cells to which MACS streptavidin beads were bound were collected from the cell suspensions using the autoMACS Pro Separator.

A solution of biotinylated HMGB1 diluted to 500 nM with HBSS was prepared again and added to the collected cells so that the density was 1E08 cells/100 μl or less, and the cells were suspended. After 30 minutes of incubation on ice, the cells were washed with 50 ml of HBSS. Solutions of streptavidin-FITC (BD) and mouse anti-rabbit IgG-PE (Southern Biotech) diluted with HBSS were prepared, and added to the cells so that the density was 1E08 cells/100 μl or less, and the cells were suspended. After incubating the cell suspensions on ice for 30 minutes, the cells were washed with 50 ml of HBSS. Next, HBSS was added to the cells in such a way that the density was 1E07 cells/100 μl or less, and they were suspended. From the cell suspensions, cells were collected using FACSAria (BD) with a gate for the fraction whose FITC and PE fluorescence intensities were both high. Upon collection. MBSS (20 mM MES, 5.3 mM KCl, 0.4 mM KH₂PO₄, 4.2 mM NaHCO₃, 0.3 mM Na₂HPO₄, 0.1% BSA, 2 mM EDTA, 5 mM glucose, 138 mM NaCl, pH 5.8) was added to tubes for the collection. Then, this was allowed to stand in the MBSS solution for 30 minutes. In the case of antibodies that readily dissociate from an antigen by decrease in pH or Ca2⁺ ion concentration, when left in MBSS at low pH and in the presence of EDTA, the antigen dissociates, resulting in decreased FITC fluorescence intensity. After being allowed to stand for 30 minutes, the cells were collected using FACSAria again, while setting a gate for cell populations whose PE fluorescence intensity was the same as the first sorting but the FITC fluorescence intensity was lower than the first sorting. The result is shown in FIG. 1. (A) shows a dot plot result for the first sorting. The cells within the gate indicated as 1 were collected. (B) shows a dot plot result for the second sorting. In the second sorting, the cells were collected separately from gates 1, 2, and 3.

When performing this cell collection method, it is unnecessary to increase the scale of subsequent screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca2⁺ ion concentration. Thus, it is possible to efficiently isolate antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration.

Culture of B Cells

The collected cells were seeded onto a 96-well microtiter plate at one cell or less/well. Activated rabbit T cell conditioned medium was added at a final concentration of 5%, and EL4 cells (European Collection of Cell Cultures) were added at about 25000 cells/well. The activated rabbit T cell conditioned medium was prepared as follows: thymuses collected from rabbits were filtered through 70 μm Cell Strainers (BD Falcon) using the plunger of a 5-ml syringe; the cells thus prepared were cultured in RPMI-1640 containing PHA (Roche), phorbol 12-myristate 13-acetate (Sigma), and 2% FBS; and the culture supernatants were frozen and stored until use at −70° C. or below. The EL4 cells to be used as feeder cells were cultured at 37° C. under 5% CO₂ for two hours or more after adding mitomycin C (Sigma) at 10 μg/ml to stop the cell growth. After leaving the culture for 5 to 7 days at 37° C. under 5% CO₂, a portion of the supernatants containing secreted antibodies was collected. Using the collected supernatants, the antibodies were assessed for their HMGB1 binding by the method described below. The cells were allowed to stand at 37° C. under 5% CO₂ until assessment of the antibodies for their HMGB1 binding.

Screening of Culture Supernatants for Monoclonal Antibodies with Desired Specificity

Screening was carried out by the ELISA method for the antigen recognition of an antibody. A streptavidin-coated 384-well plate was prepared and biotinylated HMGB1 was captured. Culture supernatants containing secreted antibodies were added to the plate. After leaving one hour at room temperature, this was washed three times with 80 μl of TBS (TAKARA) containing 2 mM CaCl₂ and 0.05% Tween-20, and then a dilution solution prepared by 40000-fold diluting Goat anti-rabbit IgG Fc HRP conjugate (BETHYL) with TBS containing 2 mM CaCl₂ was aliquoted thereto, and this was allowed to stand at room temperature for one hour. This was washed three times with 80 μl of TBS (pH 7.4) containing 2 mM CaCl₂ and 0.05% Tween-20, and a chromogenic substrate (ABTS peroxidase substrate (KPL)) was added thereto at 40 μl/well. After one hour of incubation, the absorbance at 405 nm was determined with SpectraMax from Molecular Device. The measurement result for the absorbance at 405 nm was analyzed to determine the wells with secreted antibodies that recognize the HMGB1 protein.

Screening for Antibodies Whose Dissociation Ability is Altered Depending on the Change in pH or Ca²⁺ Ion Concentration

ELISA was performed using culture supernatants to assess the presence of pH/Ca-dependent dissociation. A goat anti-rabbit IgG-Fc (BETHYL) diluted to 1 μg/ml with PBS(−) was added to a 384-well MAXISorp (Nunc). The plate was allowed to stand at room temperature for one hour or more. Then, the goat anti-rabbit IgG-Fc diluted with PBS(−) was removed from the plate, and TBS (pH 7.4) containing 1% BSA and 2 mM CaCl₂ was added thereto. The plate was allowed to stand for one hour or more. TBS (pH 7.4) containing 1% BSA and 2 mM CaCl₂ was removed from the plate, and culture supernatants were added thereto. In this step, when assessing antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ n concentration, each type of B cell culture supernatant was aliquoted to two wells in the ELISA plate. Culture supernatants were added, and the plate was allowed to stand at room temperature for one hour or more, or at 4° C. overnight, to allow the goat anti-rabbit IgG-Fc to trap antibodies in the culture supernatants. Then, the plate was washed three times with 80 μl of TBS (pH 7.4) containing 2 mM CaCl₂ and 0.05% Tween-20, and biotinylated HMGB1 was added thereto. The plate was allowed to stand at room temperature for one hour or more. This allowed biotinylated HMGB1 to bind to rabbit antibodies trapped by the goat anti-rabbit IgG-Fc. The plate was washed three times with 80 μl of TBS (pH 7.4) containing 2 mM CaCl₂ and 0.05% Tween-20 to wash off biotinylated HMGB1 that were not bound to rabbit antibodies. Then, 20 mM MES (pH 7.4) containing 150 mM NaCl and 2 mM CaCl₂(Buffer A) was added to one of the above two wells containing the same culture supernatant, and 20 mM MES (pH 5.8) containing 150 mM NaCl and 2 mM EDTA (Buffer B) was added to the other. The plate was allowed to stand at 37° C. or below for one hour or more. In the presence of Buffer A or Buffer B, biotinylated human HMGB1 dissociated from rabbit antibodies. When, due to its property, an antibody readily dissociates from an antigen at low pH, or Ca²⁺ ion is required to maintain the binding of the antibody to the antigen, the antigen more readily dissociated from the antibody on a well containing Buffer B than a well containing Buffer A. The plate was washed three times with 80 μl of TBS (pH 7.4) containing 2 mM CaCl₂ and 0.05% Tween-20. Then, 25 ng/ml of streptavidin-HRP (Genscript) prepared with TBS containing 2 mM CaCl₂ was added, and the plate was allowed to stand at room temperature for one hour. Streptavidin-HRP bound to biotinylated HMGB1 that remained without dissociating from the antibody. The plate was washed three times with 80 μl of TBS (pH 7.4) containing 2 mM CaCl₂ and 0.05% Tween-20, and a chromogenic substrate (ABTS peroxidase substrate) was added thereto. After one hour of incubation, the absorbance at 405 nm was measured with SpectraMax from Molecular Device. Based on the analysis of the result of absorbance measurement at 405 nm, when the intensity of color development in the well to which Buffer A was added was greater than that in the well to which Buffer B was added, the antibody in the culture supernatant was thought to be an antibody whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration.

This ELISA system has two features. One is that, for each B cell culture supernatant, two wells of the culture supernatant are prepared in an ELISA plate; and the antibody is allowed to bind to the antigen; and then, for dissociation of the antigen from the antibody, incubation is carried out under a condition at about pH 7.0 or above and a Ca²⁺ ion concentration of about 1 mM or higher in one well, and under a condition at about pH 6.0 or below and a low Ca²⁺ ion concentration in the other well. The presence of this incubation step enables efficient screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration. The other feature is that rabbit antibodies in the culture supernatant are trapped by the goat anti-rabbit IgG-Fc, and antigens are allowed to bind thereto. When rabbit antibodies are reacted after binding antigens to a plate, an antibody strongly bind to the antigens immobilized onto the plate with the two arms, and the binding reaction is strong. Thus, even antibodies that show pH/Ca-dependent dissociation are less likely to dissociate, and one can only obtain those which exhibit strong dependence. In contrast, when rabbit antibodies in the culture supernatant are trapped by the goat anti-rabbit IgG-Fc and antigens are allowed to bind thereto, the antigen/antibody binding is likely to occur in a one-to-one fashion. In this case, the presence or absence of the pH/Ca dependence can be determined even when the change in the dissociation ability depending on the change in pH or Ca²⁺ ion concentration is small.

The result is shown in FIGS. 2 and 3. FIG. 2 is a dot plot for the result of screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration. The Y axis indicates OD (405 nm) values under conditions of incubation with 20 mM MES (pH 7.4) containing 150 mM NaCl and 2 mM CaCl₂. The X axis indicates OD (405 nm) values under conditions of incubation with 20 mM MES (pH 5.8) containing 150 mM NaCl and 2 mM EDTA. (A) shows the result of screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration by culturing B cells from gate 1 shown in FIG. 1(B). (B) shows the result of screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration by culturing B cells from gate 2 shown in FIG. 1(B). (C) shows the result of screening for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration by culturing B cells from gate 3 shown in FIG. 1(B). The antibody that readily dissociates from the antigen when incubated at pH 5.8 in the presence of 2 mM EDTA as compared to when incubated at pH 7.4 in the presence of 2 mM Ca²⁺ is indicated by circle. The antibody for which the value is not significantly altered between conditions comprising pH 5.8 and 2 mM EDTA and pH 7.4 and 2 mM Ca²⁺ is indicated by square. FIG. 3 is a graphic representation of the numbers of clones shown in FIGS. 2(A), 2(B), and 2(C). The gray area indicates the number of clones that did not exhibit changes in antibody dissociation from antigens even when pH or the Ca²⁺ ion concentration is altered (indicated by square in (A), (B), and (C)). The dark area indicates the number of clones of antibodies that readily dissociate from antigens when pH or the Ca²⁺ ion concentration is decreased (indicated by circle in (A), (B), and (C)). When antigen-binding B cells are collected, of the antigen-binding antibodies, the proportion of antigen-binding antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration is about several percent at most, as seen in the result of (A). On the other hand, when B cells expressing antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration are enriched and collected, the proportion of antigen-binding antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration, of the antigen-binding antibodies, can be increased up to several tens percent, as seen in the result of (C). This collection method allows efficient isolation of very rare antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ ion concentration and which have physiological activity.

Sequence Identification of Variable Region L and H Chains from B Cells and Expression of Recombinant Antibodies

Based on the result of screening for monoclonal antibodies having desired specificity, or for antibodies whose dissociation ability is altered depending on the change in pH or Ca²⁺ n concentration, cells and culture supernatants were collected from a cell culture plate incubated at 37° C. under 5% CO₂, and transferred to a fresh 96-well plates by MS2000 (J-Tek). From the plate containing the collected cells and culture supernatants, the supernatants alone were transferred to another 96-well plate. Meanwhile, the plate containing the cells collected by MS2000 was frozen and stored at −70° C. or below. To construct antibody expression vectors, antibody cDNAs were prepared from the cells frozen at −70° C. PCR primers to isolate the cDNAs were designed so that they anneal to the conserved regions in the sequence of rabbit immunoglobulin (the H region and the L region). Antibody cDNAs were obtained by two collection steps using nested PCR. RNA was purified using the MagMax 96 RNA Purification Kit for microarray (Ambion). Using the purified RNA, reverse transcription and first PCR was carried out with the OneStep RT-PCR Kit (TAKARA). The primer sequences used are shown in Table 11. Then, the product of first PCR was subjected to nested PCR with PrimeSTAR HS (TAKARA). The primer sequences used for PCR are shown in Table 11. In the table, R represents a nucleotide mixture of A and G; V represents a nucleotide mixture of A, C, and G; W represents a nucleotide mixture of A and T; and Y represents a nucleotide mixture of C and T.

TABLE 1 first H CHAIN Forward AS215 AGRACCCAGCATGGACAYVA PCR (SEQ ID NO: 8) Reverse AS217 GGAYRGWATTTATTYGCCAC RCACA (SEQ ID NO: 9) L CHAIN Forward AS219 AGACRCTCACCATGGAGACT (SEQ ID NO: 10) Reverse AS221 ACTGGCTCCGGGAGGTA (SEQ ID NO: 11) nested H CHAN Forward AS365 CACCATGGAGACTGGGC PCR (SEQ ID NO: 12) Reverse AS368 GGAGGAGACGGTGAC (SEQ ID NO: 13) L CHAIN Forward AS359 ATGGACACGAGGGCCC (SEQ ID NO: 14) Reverse AS362 TTTGACCACCACCTCGGTC (SEQ ID NO: 15)

Cassette vectors were constructed by inserting the sequences of antibody constant regions into an animal cell expression vector, and they were used to construct antibody expression vectors. The following two types of cassette vectors were constructed: a vector carrying the sequence of the H chain constant region of a rabbit antibody; and a vector carrying the sequence of the L chain constant region of a rabbit antibody. The vector carrying the sequence of an H chain constant region has an inserted ampicillin resistance gene, while the vector carrying the sequence of an L chain constant region has an inserted kanamycin resistance gene. These two types of vectors have a partial sequence overlap with the nested PCR primer sequences. Using the In-Fusion PCR cloning Kit (Clontech), the nested PCR products are incorporated into the cassette vectors introduced with the sequences of the antibody constant regions to construct expression vectors containing the full-length rabbit antibody genes. The nested PCR products were inserted into vectors using an In-Fusion PCR cloning Kit from Clontech, and then transformed into bacteria for plasmid transmission and production. The transformed bacteria were cultured in LB media containing ampicillin or kanamycin. After purification of plasmids from the grown bacteria using the 96-well EndoFree ezFilter Plasmid Miniprep Kit (Biomiga), antibodies were prepared according to Reference Example 1.

Example 2 Determination of the Affinity and pH/Ca Dependency of Anti-HMGB1 Antibody Preparation of MedG4-IgG1 Antibody

MedG4H-IgG1 (SEQ ID NO: 36) and MedG4L-CK (SEQ ID NO: 37) were designed by linking the VH region (WO2007/084253, SEQ ID NO: 19) and VL region (WO2007/084253, SEQ ID NO: 17) of the G4 antibody described in WO2007/084253 to human IgG1 constant region and human Igκ constant region, respectively. To prepare MedG4-IgG1, which is an anti-HMGB1 antibody. DNAs encoding those described above were constructed using genetic engineering techniques, and expressed in animal cells by a method known to those skilled in the art.

Assessment of Prepared Antibodies for the pH- and pH/Ca-Dependent Binding Ability to Human HMGB1

Prepared antibodies were assessed for the presence of pH- and pH/Ca-dependent binding ability using BiacoreT100 and T200 (GE Healthcare). The plasma condition was set to be pH 7.4 and a calcium ion concentration of 1.2 mM. Two types of intraendosomal conditions were set to be: pH 5.8 and a calcium ion concentration of 1.2 mM; and pH 5.8 and a calcium ion concentration of 3 μM. An appropriate amount of Protein A (Invitrogen) was immobilized onto Sensor chip CM4 (GE Healthcare) by the amine coupling method and antibodies of interest were captured thereon. The antigen used was human HMGB1. Measurements were carried out using three types of running buffers (#1: 20 mmol/l ACES, 150 mmol/l NaCl, 0.05% (w/v) Tween20, 2 mmol/l CaCl₂, pH 7.4; #2: 20 mmol/l ACES, 150 mmol/l NaCl, 0.05% (w/v) Tween20, 2 mmol/l CaCl₂, pH 5.8: #3: 20 mmol/l ACES, 150 mmol/l NaCl, 0.05% (w/v) Tween20, 3 μmol/l CaCl₂, pH 5.8). Human HMGB1 was diluted using the respective running buffers.

HMG233-IgG1, HMG236-IgG1, HMG481-IgG1, and HMG487-IgG1

Antibodies diluted with a running buffer were captured onto a sensor chip by injecting at a flow rate of 10 μl/min for one minute. Then, a solution of diluted human HMGB1 (500 nM) and a running buffer (as a reference solution) were injected at a flow rate of 10 μl/min for one minute to interact with the captured antibodies. Then, a running buffer was injected at a flow rate of 10 μl/min for one minute to observe the dissociation of human HMGB1. Finally, 10 mmol/1 glycine-HCl (pH 1.5) was injected at a flow rate of 30 μl/min for 30 seconds to regenerate the sensor chip.

Sensorgrams obtained by the measurement are shown in FIGS. 4-1 and 4-2, in which the quantity of each antibody captured has been converted to 100 RU. Since they are a box-shaped sensorgram with rapid convergence to an equilibrium state, the equilibrium value (i.e., binding amount) during injection of human HMGB1 reflects the dissociation constant KD (M). As to HMG233-IgG1 and HMG236-IgG1, each antibody showed a significant decrease in the amount of binding to human HMGB1 under the condition of pH 5.8 and 3 μM Ca as compared to the conditions of pH 7.4 and 1.2 mM Ca and of pH 5.8 and 1.2 mM Ca. Regarding HMG481-IgG1 and HMG487-IgG1, each antibody exhibited a significant decrease in the amount of binding to human HMGB1 under the conditions of pH 5.8 and 1.2 mM Ca, and of pH 5.8 and 3 μM Ca as compared to the condition of pH 7.4 and 1.2 mM Ca.

HMG446-IgG1 and MedG4-IgG1

With respect to HMG446-IgG1 and MedG4-IgG1, an antibody diluted with a running buffer was captured onto a sensor chip by injecting at a flow rate of 10 μl/min for one minute, and then a solution of diluted human HMGB1 and a running buffer (as a reference solution) were injected at a flow rate of 10 μl/min for one minute to interact with the captured antibody. Next, a running buffer was injected at a flow rate of 10 μl/min for two minutes to observe the dissociation of human HMGB1. Finally, 10 mmol glycine-HCl (pH 1.5) was injected at a flow rate of 30 μl/min for 30 seconds to regenerate the sensor chip.

Regarding MedG4-IgG1, a sensorgram obtained by the measurement was analyzed by curve fitting. A 1:1 binding model is used for the reaction model equation. The binding rate constant ka (1/Ms) and dissociation rate constant kd (1/s), which are kinetic parameters, were calculated, and based on the values, the dissociation constant KD (M) was calculated for each antibody for dissociation from human HMGB1. Regarding HMG446-IgG1, the dissociation constant KD (M) was calculated by applying a steady state affinity model to the sensorgram obtained by the measurement. Each parameter was calculated using Biacore T200 Evaluation Software (GE Healthcare). Meanwhile, the pH dependence was determined by dividing KD (M) at pH 5.8 and 1.2 mM Ca by KD (M) at pH 7.4 and 1.2 mM Ca, whereas the pH/Ca dependence was determined by dividing KD (M) at pH 5.8 and 3 μM Ca by KD (M) at pH 7.4 and 1.2 mM.

The analysis result is summarized in Table 12. The KD (M) of HMG446-IgG1 at pH 7.4 and 1.2 mM Ca was calculated to be 220 nM. The KD (M) to human HMGB1 was increased by 50 times (the affinity was reduced by 50 times) by the change from pH 7.4, 1.2 mM Ca to pH 5.8, 1.2 mM Ca, and it was increased by 82 times (the affinity was reduced by 82 times) by the change to pH 5.8, 3 μM Ca. This demonstrates that the affinity for human HMGB1 is reduced under the intraendosomal condition compared to the plasma condition. Meanwhile, the KD (M) of MedG4-IgG1 was calculated to be 96 nM at pH 7.4 and 1.2 mM Ca, and 15 nM at pH 5.8 and 1.2 mM Ca and 3 μM Ca. This demonstrates that the affinity for human HMGB1 is increased under the intraendosomal condition compared to the plasma condition, suggesting that MedG4-IgG1 is less likely to release HMGB1 in the endosome.

TABLE 12 ANTIBODY NAME CONDITION K_(D) (M) DEPENDENCY MedG4 pH 7.4, 1.2 mM Ca 96 nM pH 5.8, 1.2 mM Ca 15 nM 0.15 TIMES (pH-DEPENDENT) pH 5.8, 3 μM Ca 15 nM 0.15 TIMES (pH/Ca-DEPENDENT) HMG446 pH 7.4, 1.2 mM Ca 220 nM  pH 5.8, 1.2 mM Ca 1.1 μM    50 TIMES (pH-DEPENDENT) pH 5.8, 3 μM Ca 1.8 μM    82 TIMES (pH/Ca-DEPENDENT)

Example 3 Assessment for the Binding Between HMGB1 and the Cell Surface Receptor ELISA for the Binding of HMGB1 to RAGE-Fc

A solution containing 5 μg/ml recombinant human RAGE-Fc fusion protein (R&D SYSTEMS) in PBS was added to each well of an ELISA plate at 20 μl/well. The plate was incubated at 4° C. overnight. Then, the plate was blocked with 100 μl of 5% skim milk at 37° C. for one hour, and washed four times with PBS/Tween. In another plate, 4 μg/ml HMGB1 was pre-incubated with 100 μg/ml anti-HMGB1 antibody or a buffer in the presence of 2.5% skim milk at room temperature for one hour, and this was transferred to the RAGE-coated, blocked plate. Then, the plate was incubated at 4° C. overnight, and washed four times with PBS/Tween. To detect HMGB1 bound to the immobilized RAGE-Fc, a peroxidase-labeled mouse anti-HMGB1 monoclonal antibody was added to each well, and the plate was incubated at room temperature for two hours. Then, the plate was washed five times, and 20 μl of the chromogenic agent TMB was added thereto. The absorbance at 450 nm in the plate was measured.

It was confirmed that the anti-HMGB1 antibody does not inhibit the binding between HMGB1 and the peroxidase-labeled mouse anti-HMGB1 monoclonal antibody used for detection, by allowing the anti-HMGB1 antibody to compete the peroxidase-labeled mouse anti-HMGB1 monoclonal antibody in an HMGB1-immobilized plate.

ELISA for the Binding of HMGB1 to TLR4/MD-2

A solution of 5 μg/ml recombinant human TLR4/MD-2 protein (R&D SYSTEMS) in PBS was added to each well of an ELISA plate at 20 μl/well. The plate was incubated at 4° C. overnight. Then, the plate was blocked with 100 μl of 5% skim milk at 37° C. for one hour, and washed four times with PBS:Tween. In another plate, 10 μg/ml HMGB1 was pre-incubated with 100 μg/ml anti-HMGB1 antibody or a buffer in the presence of 2.5% skim milk at room temperature for one hour, and this was transferred to the TLR4/MD-2-coated, blocked plate. Then, the plate was incubated at room temperature for two hours, and washed four times with PBS/Tween. To detect HMGB1 bound to the immobilized TLR4/MD-2, 1 μg/ml peroxidase-labeled mouse anti-HMGB1 monoclonal antibody was added to each well, and the plate was incubated at room temperature for two hours. Then, the plate was washed five times with PBS/Tween, and 20 μl of the chromogenic agent TMB was added thereto. The absorbance at 450 nm in the plate was measured.

It was confirmed that the anti-HMGB1 antibody does not inhibit the binding between HMGB1 and the peroxidase-labeled mouse anti-HMGB1 monoclonal antibody used for detection, by allowing the anti-HMGB1 antibody to compete the peroxidase-labeled mouse anti-HMGB1 monoclonal antibody in an HMGB1-immobilized plate.

Results

Both RAGE and TLR4 have been identified as putative receptors for HMGB1. Some anti-HMGB1 antibodies were assessed by ELISA assay for their ability to inhibit the binding between HMGB1 and the RAGE-Fc fusion product or TLR4/MD-2 fusion product.

By setting the value determined under the condition in the absence of the anti-HMGB1 antibody as 100, a relative value was determined for each of RAGE and TLR4 from the value determined under each condition in the presence of the anti-HMGB1 antibody. The values are shown in FIGS. 5 and 6. Anti-HMGB1 antibodies with a value less than 100 were determined to have the ability to inhibit the binding to each receptor. Of the antibodies subjected to RAGE ELISA, HMG233-IgG1 and HMG236-IgG1 inhibited the binding of HMGB1 to RAGE. The percent inhibition was 53.1% for HMG233-IgG1, and 64.1% for HMG236-IgG1. Of the antibodies subjected to TLR4/MD-2 ELISA, HMG481-IgG1, HMG487-IgG1, and HMG446-IgG1 inhibited the binding of HMGB1 to TLR4/MD-2. The percent inhibition was 93.5% for HMG481-IgG1, 75.7% for HMG487-IgG1, and 81.3% for HMG446-IgG1, HMG233-IgG1 and HMG236-IgG1 did not inhibit the binding between HMGB1 and TLR4/MD-2. Meanwhile, HMG481-IgG1, HMG487-IgG1, and HMG446-IgG1 did not inhibit the binding between HMGB1 and RAGE.

The present invention demonstrated that, of anti-HMGB1 antibodies, some antibodies inhibited the binding of HMGB1 to RAGE but not the binding to TLR4, and that some antibody inhibited the binding of HMGB1 to TLR4/MD-2 but not the binding to RAGE.

Example 4 Improvement of the Effect to Accelerate the Elimination of Human HMGB1 by the pH-Dependent Anti-Human HMGB1 Antibody In Vivo Test Using Normal Mice

Human HMGB1 and anti-human HMGB1 antibody were simultaneously administered to normal mice (C57BL/6J mouse, Charles River Japan) to assess the in vivo kinetics of human HMGB1 and the anti-human HMGB1 antibody. A mixed solution of human HMGB1 (0.1 mg/ml) and the anti-human HMGB1 antibody (1 mg/ml MedG4-IgG1, 2.05 mg/ml HMG446) was administered at 10 mL/kg once into the tail vein. The antibody concentration in this mixed solution was adopted as a concentration that allows 99.0% or more of human HMGB1 contained in the solution to bind to the antibody. Blood was collected at 5 minutes, 10 minutes, 15 minutes, one hour, 4 hours, 2 days, and 7 days after administration. The collected blood was allowed to stand for two hours, and then centrifuged at 12,000 rpm and 4° C. for 5 minutes to obtain sera. The isolated sera were stored in a freezer set at −20° C. or below until use. Herein, MedG4-IgG1 is sometimes referred to as “med G4”, while HMG446-IgG1 is sometimes referred to as “HMG446-G1”.

Determination of Anti-Human HMGB1 Antibody Concentration in Serum by ELISA

Anti-human HMGB1 antibody concentrations in mouse sera were determined by ELISA. First, to prepare an anti-human IgG-immobilized plate, Anti-Human IgG (γ-chain specific) F(ab′)2 Fragment of Antibody (SIGMA) was aliquoted into a Nunc-Immuno Plate, MaxiSorp (Nalge nunc International), and the plate was allowed to stand at 4° C. overnight. Standard curve samples (serum concentrations of 3.2, 1.6, 0.8, 0.4, 0.2, 0.1, and 0.05 μg/ml) and assay samples of mouse serum diluted 100 times or more were prepared. 150 μl of 2000 ng/ml human HMGB1 was added to 150 μl of the standard curve samples and assay samples. This was allowed to stand at room temperature for one hour, and then aliquoted into the anti-human IgG-immobilized plate. The plate was allowed to stand at room temperature for one hour. Then. Goat Anti-Human IgG (γ chain specific) Biotin (BIOT) Conjugate (Southern Biotech Association) was reacted at room temperature for one hour. Next, Streptavidin-PolyHRP80 (Stereospecific Detection Technologies) was reacted at room temperature for one hour. Chromogenic reaction was performed using TMB One Component HRP Microwell Substrate (BioFX Laboratories) as a substrate. After terminating the reaction with 1N sulfuric acid (Showa Chemical), the absorbance at 450 nm was measured with a microplate reader. The anti-human HMGB1 antibody concentrations in mouse sera were determined based on the absorbance of the standard curve using the analysis software SOFTmax PRO (Molecular Devices). A time course of anti-human HMGB1 antibody concentration in the sera of mice after intravenous administration, which was measured by the above method, is shown in FIG. 8.

Measurement of Human HMGB1 Concentration in Serum by ELISA

Human HMGB1 concentrations in mouse sera were measured using HMGB1 ELISA Kit II (shino-test). Standard curve samples with a serum concentration of 12800, 6400, 3200, 1600, 800, 400, or 200 μg/ml, and assay samples of mouse sera diluted 100 times or more were prepared, and mixed with an equal volume of 40 μg/ml HMG446 solution (in the presence of HMG446-IgG1 or HMG446-F1) or 20 μg/ml MedG4-IgG1 solution (in the presence of MedG4-IgG1). After one hour of incubation at room temperature, the mixtures were aliquoted in the attached, immobilized plate. The plate was incubated at 37° C. for 20 to 24 hours. Then, the attached, labeled antibody solution was reacted at 25° C. for two hours. After 30 minutes of reaction with a chromogenic reagent, the reaction was stopped by adding a stop solution. Then, the absorbance at 450 nm was measured using a microplate reader. The human HMGB1 concentrations in mouse sera were calculated based on the absorbance of the standard curve using the analysis software SOFTmax PRO (Molecular Devices). A time course of human HMGB1 concentration in the sera of mice after intravenous administration, which was measured by the above method, is shown in FIG. 7.

The Effect of pH/Ca-Dependent Binding to Human HMGB1

HMG446-IgG1 whose human HMGB1-binding activity is decreased at acidic pH or low calcium ion concentration and MedG4-IgG1 whose human HMGB1-binding activity is not decreased at acidic pH or low calcium ion concentration were tested in vivo, and the results were compared to each other. As shown in FIG. 8, the pharmacokinetics of the two antibodies showed linearity. Meanwhile, as shown in FIG. 7, it was revealed that, when HMGB1 was administered in combination with HMG446-IgG1 that binds to human HMGB1 in a pH-dependent manner, HMG446-IgG1 accelerated the elimination of HMGB1 as compared to when MedG4-IgG1 was administered in combination with HMGB1. Thus, it was demonstrated that, by conferring the pH-dependent human HMGB1-binding ability, the serum HMGB1 concentration can be decreased by about 4.0 times one day after administration.

The Effect of FcRn Binding at Neutral Conditions (pH 7.4)

In addition to HMG446-IgG1, HMG446-F1 resulting from introducing an amino acid substitution into the IgG Fc region of HMG446-IgG1, was tested in vivo using mice. The test result was compared to that for HMG446-IgG1. As shown in FIG. 8, the serum antibody concentration of HMG446-F1 whose mouse FcRn binding was enhanced under a neutral condition (pH 7.4) was lower by about 1.2 times than that of HMG446-IgG1 15 minutes after administration.

As shown in FIG. 7, it was demonstrated that HMGB1, when administered in combination with HMG446-F1 whose mouse FcRn binding was enhanced under a neutral condition (pH 7.4), was eliminated more rapidly as compared to when HMGB1 was administered in combination with HMG446-IgG1. HMG446-F1 reduced the serum HMGB1 concentration by about 2.4 times in 15 minutes as compared to HMG446-IgG1. Thus, it was demonstrated that the serum human HMGB1 concentration can be reduced by conferring the mouse FcRn-binding ability under a neutral condition (pH 7.4). As described above, the antibody concentration in serum was reduced by conferring the ability to bind to mouse FcRn under a neutral condition (pH 7.4). However, the achieved effect to decrease the serum HMGB1 concentration exceeded the decrease in antibody concentration.

The above results suggest that, by administering an antibody whose binding activity to human HMGB1 is reduced under an acidic pH or low calcium ion concentration condition, the elimination of human HMGB1 can be accelerated as compared to when administering an antibody whose binding activity to human HMGB1 is not reduced at an acidic pH or low calcium ion concentration condition, and this effect is enhanced depending on the mouse FcRn-binding ability under a neutral condition (pH 7.4).

Example 5 Production of Various Antibody Fc Variants with Increased Binding Affinity for Human FcRn at Neutral pH Production of Fc Variants

To increase the binding affinity for human FcRn in a neutral pH range, various substitutions were introduced into the antibody Fv4-IgG1 that comprise the H chain and L chain which are, respectively. VH3-IgG1 and VL3-CK described as SEQ ID NOs: 6 and 7 in WO2009/125825. Specifically, the amino acid substitutions shown in Table 13-1 to 13-14 were introduced into the heavy chain constant region of Fv4-IgG1 to create Fc variants (the amino acid numbers for mutation sites are shown according to EU numbering). Amino acid substitutions were introduced according to the method known to those skilled in the art, which is described in Reference Example 1.

Variants containing the prepared heavy chains and the light chain L(WT) described as SEQ ID NO: 5 in WO2009/125825 were expressed and purified by the method known to those skilled in the art, which is described in Reference Example 1.

Assessment of Human FcRn Binding

The binding between the antibody and human FcRn under a neutral condition (pH 7.0) was analyzed with Biacore. The results are shown in Table 13-1 to 13-14.

TABLE 13-1 VARIANT NAME KD (M) AMINO ACID SUBSTITUTION F1 8.10E−07 N434W F2 3.20E−06 M252Y/S254T/T256E F3 2.50E−06 N434Y F4 5.80E−06 N434S F5 6.80E−06 N434A F7 5.60E−06 M252Y F8 4.20E−06 M252W F9 1.40E−07 M252Y/S254T/T256E/N434Y F10 6.90E−08 M252Y/S254T/T256E/N434W F11 3.10E−07 M252Y/N434Y F12 1.70E−07 M252Y/N434W F13 3.20E−07 M252W/N434Y F14 1.80E−07 M252W/N434W F19 4.60E−07 P257L/N434Y F20 4.60E−07 V308F/N434Y F21 3.00E−08 M252Y/V308P/N434Y F22 2.00E−06 M428L/N434S F25 9.20E−09 M252Y/S254T/T256E/V308P/N434W F26 1.00E−06 I332V F27 7.40E−06 G237M F29 1.40E−06 I332V/N434Y F31 2.80E−06 G237M/V308F F32 8.00E−07 S254T/N434W F33 2.30E−06 S254T/N434Y F34 2.80E−07 T256E/N434W F35 8.40E−07 T256E/N434Y F36 3.60E−07 S254T/T256E/N434W F37 1.10E−06 S254T/T256E/N434Y F38 1.00E−07 M252Y/S254T/N434W F39 3.00E−07 M252Y/S254T/N434Y F40 8.20E−08 M252Y/T256E/N434W F41 1.50E−07 M252Y/T256E/N434Y F42 1.00E−06 M252Y/S254T/T256E/N434A F43 1.70E−06 M252Y/N434A F44 1.10E−06 M252W/N434A F47 2.40E−07 M252Y/T256Q/N434W F48 3.20E−07 M252Y/T256Q/N434Y F49 5.10E−07 M252F/T256D/N434W F50 1.20E−06 M252F/T256D/N434Y F51 8.10E−06 N434F/Y436H F52 3.10E−06 H433K/N434F/Y436H F53 1.00E−06 I332V/N434W F54 8.40E−08 V308P/N434W F56 9.40E−07 I332V/M428L/N434Y F57 1.10E−05 G385D/Q386P/N389S F58 7.70E−07 G385D/Q386P/N389S/N434W F59 2.40E−06 G385D/Q386P/N389S/N434Y F60 1.10E−05 G385H F61 9.70E−07 G385H/N434W F62 1.90E−06 G385H/N434Y F63 2.50E−06 N434F F64 5.30E−06 N434H F65 2.90E−07 M252Y/S254T/T256E/N434F F66 4.30E−07 M252Y/S254T/T256E/N434H F67 6.30E−07 M252Y/N434F F68 9.30E−07 M252Y/N434H F69 5.10E−07 M428L/N434W F70 1.50E−06 M428L/N434Y F71 8.30E−08 M252Y/S254T/T256E/M428L/N434W F72 2.00E−07 M252Y/S254T/T256E/M428L/N434Y

Table 13-2 is the continuation of Table 13-1.

TABLE 13-2 F73 1.70E−07 M252Y/M428L/N434W F74 4.60E−07 M252Y/M428L/N434Y F75 1.40E−06 M252Y/M428L/N434A F76 1.00E−06 M252Y/S254T/T256E/M428L/N434A F77 9.90E−07 T256E/M428L/N434Y F78 7.80E−07 S254T/M428L/N434W F79 5.90E−06 S254T/T256E/N434A F80 2.70E−06 M252Y/T256Q/N434A F81 1.60E−06 M252Y/T256E/N434A F82 1.10E−06 T256Q/N434W F83 2.60E−06 T256Q/N434Y F84 2.80E−07 M252W/T256Q/N434W F85 5.50E−07 M252W/T256Q/N434Y F86 1.50E−06 S254T/T256Q/N434W F87 4.30E−06 S254T/T256Q/N434Y F88 1.90E−07 M252Y/S254T/T256Q/N434W F89 3.60E−07 M252Y/S254T/T256Q/N434Y F90 1.90E−08 M252Y/T256E/V308P/N434W F91 4.80E−08 M252Y/V308P/M428L/N434Y F92 1.10E−08 M252Y/S254T/T256E/V308P/M428L/N434W F93 7.40E−07 M252W/M428L/N434W F94 3.70E−07 P257L/M428L/N434Y F95 2.60E−07 M252Y/S254T/T256E/M428L/N434F F99 6.20E−07 M252Y/T256E/N434H F101 1.10E−07 M252W/T256Q/P257L/N434Y F103 4.40E−08 P238A/M252Y/V308P/N434Y F104 3.70E−08 M252Y/D265A/V308P/N434Y F105 7.50E−08 M252Y/T307A/V308P/N434Y F106 3.70E−08 M252Y/V303A/V308P/N434Y F107 3.40E−08 M252Y/V308P/D376A/N434Y F108 4.10E−08 M252Y/V305A/V308P/N434Y F109 3.20E−08 M252Y/V308P/Q311A/N434Y F111 3.20E−08 M252Y/V308P/K317A/N434Y F112 6.40E−08 M252Y/V308P/E380A/N434Y F113 3.20E−08 M252Y/V308P/E382A/N434Y F114 3.80E−08 M252Y/V308P/S424A/N434Y F115 6.60E−06 T307A/N434A F116 8.70E−06 E380A/N434A F118 1.40E−05 M428L F119 5.40E−06 T250Q/M428L F120 6.30E−08 P257L/V308P/M428L/N434Y F121 1.50E−08 M252Y/T256E/V308P/M428L/N434W F122 1.20E−07 M252Y/T256E/M428L/N434W F123 3.00E−08 M252Y/T256E/V308P/N434Y F124 2.90E−07 M252Y/T256E/M428L/N434Y F125 2.40E−08 M252Y/S254T/T256E/V308P/M428L/N434Y F128 1.70E−07 P257L/M428L/N434W F129 2.20E−07 P257A/M428L/N434Y F131 3.00E−06 P257G/M428L/N434Y F132 2.10E−07 P257I/M428L/N434Y F133 4.10E−07 P257M/M428L/N434Y F134 2.70E−07 P257N/M428L/N434Y F135 7.50E−07 P257S/M428L/N434Y F136 3.80E−07 P257T/M428L/N434Y F137 4.60E−07 P257V/M428L/N434Y F139 1.50E−08 M252W/V308P/N434W F140 3.60E−08 S239K/M252Y/V308P/N434Y F141 3.50E−08 M252Y/S298G/V308P/N434Y F142 3.70E−08 M252Y/D270F/V308P/N434Y F143 2.00E−07 M252Y/V308A/N434Y F145 5.30E−08 M252Y/V308F/N434Y

Table 13-3 is the continuation of Table 13-2.

TABLE 13-3 F147 2.40E−07 M252Y/V308I/N434Y F149 1.90E−07 M252Y/V308L/N434Y F150 2.00E−07 M252Y/V308M/N434Y F152 2.70E−07 M252Y/V308Q/N434Y F154 1.80E−07 M252Y/V308T/N434Y F157 1.50E−07 P257A/V308P/M428L/N434Y F158 5.90E−08 P257T/V308P/M428L/N434Y F159 4.40E−08 P257V/V308P/M428L/N434Y F160 8.50E−07 M252W/M428I/N434Y F162 1.60E−07 M252W/M428Y/N434Y F163 4.20E−07 M252W/M428F/N434Y F164 3.70E−07 P238A/M252W/N434Y F165 2.90E−07 M252W/D265A/N434Y F166 1.50E−07 M252W/T307Q/N434Y F167 2.90E−07 M252W/V303A/N434Y F168 3.20E−07 M252W/D376A/N434Y F169 2.90E−07 M252W/V305A/N434Y F170 1.70E−07 M252W/Q311A/N434Y F171 1.90E−07 M252W/D312A/N434Y F172 2.20E−07 M252W/K317A/N434Y F173 7.70E−07 M252W/E380A/N434Y F174 3.40E−07 M252W/E382A/N434Y F175 2.70E−07 M252W/S424A/N434Y F176 2.90E−07 S239K/M252W/N434Y F177 2.80E−07 M252W/S298G/N434Y F178 2.70E−07 M252W/D270F/N434Y F179 3.10E−07 M252W/N325G/N434Y F182 6.60E−08 P257A/M428L/N434W F183 2.20E−07 P257T/M428L/N434W F184 2.70E−07 P257V/M428L/N434W F185 2.60E−07 M252W/I332V/N434Y F188 3.00E−06 P257I/Q311I F189 1.90E−07 M252Y/T307A/N434Y F190 1.10E−07 M252Y/T307Q/N434Y F191 1.60E−07 P257L/T307A/M428L/N434Y F192 1.10E−07 P257A/T307A/M428L/N434Y F193 8.50E−08 P257T/T307A/M428L/N434Y F194 1.20E−07 P257V/T307A/M428L/N434Y F195 5.60E−08 P257L/T307Q/M428L/N434Y F196 3.50E−08 P257A/T307Q/M428L/N434Y F197 3.30E−08 P257T/T307Q/M428L/N434Y F198 4.80E−08 P257V/T307Q/M428L/N434Y F201 2.10E−07 M252Y/T307D/N434Y F203 2.40E−07 M252Y/T307F/N434Y F204 2.10E−07 M252Y/T307G/N434Y F205 2.00E−07 M252Y/T307H/N434Y F206 2.30E−07 M252Y/T307I/N434Y F207 9.40E−07 M252Y/T307K/N434Y F208 3.90E−07 M252Y/T307L/N434Y F209 1.30E−07 M252Y/T307M/N434Y F210 2.90E−07 M252Y/T307N/N434Y F211 2.40E−07 M252Y/T307P/N434Y F212 6.80E−07 M252Y/T307R/N434Y F213 2.30E−07 M252Y/T307S/N434Y F214 1.70E−07 M252Y/T307V/N434Y F215 9.60E−08 M252Y/T307W/N434Y F216 2.30E−07 M252Y/T307Y/N434Y F217 2.30E−07 M252Y/K334L/N434Y F218 2.60E−07 M252Y/G385H/N434Y F219 2.50E−07 M252Y/T289H/N434Y F220 2.60E−07 M252Y/Q311H/N434Y

Table 13-4 is the continuation of Table 13-3.

TABLE 13-4 F221 3.10E−07 M252Y/D312H/N434Y F222 3.40E−07 M252Y/N315H/N434Y F223 2.70E−07 M252Y/K360H/N434Y F225 1.50E−06 M252Y/L314R/N434Y F226 5.40E−07 M252Y/L314K/N434Y F227 1.20E−07 M252Y/N286E/N434Y F228 2.30E−07 M252Y/L309E/N434Y F229 5.10E−07 M252Y/R255E/N434Y F230 2.50E−07 M252Y/P387E/N434Y F236 8.90E−07 K248I/M428L/N434Y F237 2.30E−07 M252Y/M428A/N434Y F238 7.40E−07 M252Y/M428D/N434Y F240 7.20E−07 M252Y/M428F/N434Y F241 1.50E−06 M252Y/M428G/N434Y F242 8.50E−07 M252Y/M428H/N434Y F243 1.80E−07 M252Y/M428I/N434Y F244 1.30E−06 M252Y/M428K/N434Y F245 4.70E−07 M252Y/M428N/N434Y F246 1.10E−06 M252Y/M428P/N434Y F247 4.40E−07 M252Y/M428Q/N434Y F249 6.40E−07 M252Y/M428S/N434Y F250 2.90E−07 M252Y/M428T/N434Y F251 1.90E−07 M252Y/M428V/N434Y F252 1.00E−06 M252Y/M428W/N434Y F253 7.10E−07 M252Y/M428Y/N434Y F254 7.50E−08 M252W/T307Q/M428Y/N434Y F255 1.10E−07 M252W/Q311A/M428Y/N434Y F256 5.40E−08 M252W/T307Q/Q311A/M428Y/N434Y F257 5.00E−07 M252Y/T307A/M428Y/N434Y F258 3.20E−07 M252Y/T307Q/M428Y/N434Y F259 2.80E−07 M252Y/D270F/N434Y F260 1.30E−07 M252Y/T307A/Q311A/N434Y F261 8.40E−08 M252Y/T307Q/Q311A/N434Y F262 1.90E−07 M252Y/T307A/Q311H/N434Y F263 1.10E−07 M252Y/T307Q/Q311H/N434Y F264 2.80E−07 M252Y/E382A/N434Y F265 6.80E−07 M252Y/E382A/M428Y/N434Y F266 4.70E−07 M252Y/T307A/E382A/M428Y/N434Y F267 3.20E−07 M252Y/T307Q/E382A/M428Y/N434Y F268 6.30E−07 P238A/M252Y/M428F/N434Y F269 5.20E−07 M252Y/V305A/M428F/N434Y F270 6.60E−07 M252Y/N325G/M428F/N434Y F271 6.90E−07 M252Y/D376A/M428F/N434Y F272 6.80E−07 M252Y/E380A/M428F/N434Y F273 6.50E−07 M252Y/E382A/M428F/N434Y F274 7.60E−07 M252Y/E380A/E382A/M428F/N434Y F275 4.20E−08 S239K/M252Y/V308P/E382A/N434Y F276 4.10E−08 M252Y/D270F/V308P/E382A/N434Y F277 1.30E−07 S239K/M252Y/V308P/M428Y/N434Y F278 3.00E−08 M252Y/T307Q/V308P/E382A/N434Y F279 6.10E−08 M252Y/V308P/Q311H/E382A/N434Y F280 4.10E−08 S239K/M252Y/D270F/V308P/N434Y F281 9.20E−08 M252Y/V308P/E382A/M428F/N434Y F282 2.90E−08 M252Y/V308P/E382A/M428L/N434Y F283 1.00E−07 M252Y/V308P/E382A/M428Y/N434Y F284 1.00E−07 M252Y/V308P/M428Y/N434Y F285 9.90E−08 M252Y/V308P/M428F/N434Y F286 1.20E−07 S239K/M252Y/V308P/E382A/M428Y/N434Y F287 1.00E−07 M252Y/V308P/E380A/E382A/M428F/N434Y F288 1.90E−07 M252Y/T256E/E382A/N434Y F289 4.80E−07 M252Y/T256E/M428Y/N434Y

Table 13-5 is the continuation of Table 13-4.

TABLE 13-5 F290 4.60E−07 M252Y/T256E/E382A/M428Y/N434Y F292 2.30E−08 S239K/M252Y/V308P/E382A/M428I/N434Y F293 5.30E−08 M252Y/V308P/E380A/E382A/M428I/N434Y F294 1.10E−07 S239K/M252Y/V308P/M428F/N434Y F295 6.80E−07 S239K/M252Y/E380A/E382A/M428F/N434Y F296 4.90E−07 M252Y/Q311A/M428Y/N434Y F297 5.10E−07 M252Y/D312A/M428Y/N434Y F298 4.80E−07 M252Y/Q311A/D312A/M428Y/N434Y F299 9.40E−08 S239K/M252Y/V308P/Q311A/M428Y/N434Y F300 8.30E−08 S239K/M252Y/V308P/D312A/M428Y/N434Y F301 7.20E−08 S239K/M252Y/V308P/Q311A/D312A/M428Y/N434Y F302 1.90E−07 M252Y/T256E/T307P/N434Y F303 6.70E−07 M252Y/T307P/M428Y/N434Y F304 1.60E−08 M252W/V308P/M428Y/N434Y F305 2.70E−08 M252Y/T256E/V308P/E382A/N434Y F306 3.60E−08 M252W/V308P/E382A/N434Y F307 3.60E−08 S239K/M252W/V308P/E382A/N434Y F308 1.90E−08 S239K/M252W/V308P/E382A/M428Y/N434Y F310 9.40E−08 S239K/M252W/V308P/E382A/M428I/N434Y F311 2.80E−08 S239K/M252W/V308P/M428F/N434Y F312 4.50E−07 S239K/M252W/E380A/E382A/M428F/N434Y F313 6.50E−07 S239K/M252Y/T307P/M428Y/N434Y F314 3.20E−07 M252Y/T256E/Q311A/D312A/M428Y/N434Y F315 6.80E−07 S239K/M252Y/M428Y/N434Y F316 7.00E−07 S239K/M252Y/D270F/M428Y/N434Y F317 1.10E−07 S239K/M252Y/D270F/V308P/M428Y/N434Y F318 1.80E−08 S239K/M252Y/V308P/M428I/N434Y F320 2.00E−08 S239K/M252Y/V308P/N325G/E382A/M428I/N434Y F321 3.20E−08 S239K/M252Y/D270F/V308P/N325G/N434Y F322 9.20E−08 S239K/M252Y/D270F/T307P/V308P/N434Y F323 2.70E−08 S239K/M252Y/T256E/D270F/V308P/N434Y F324 2.80E−08 S239K/M252Y/D270F/T307Q/V308P/N434Y F325 2.10E−08 S239K/M252Y/D270F/T307Q/V308P/Q311A/N434Y F326 7.50E−08 S239K/M252Y/D270F/T307Q/Q311A/N434Y F327 6.50E−08 S239K/M252Y/T256E/D270F/T307Q/Q311A/N434Y F328 1.90E−08 S239K/M252Y/D270F/V308P/M428I/N434Y F329 1.20E−08 S239K/M252Y/D270F/N286E/V308P/N434Y F330 3.60E−08 S239K/M252Y/D270F/V308P/L309E/N434Y F331 3.00E−08 S239K/M252Y/D270F/V308P/P387E/N434Y F333 7.40E−08 S239K/M252Y/D270F/T307Q/L309E/Q311A/N434Y F334 1.90E−08 S239K/M252Y/D270F/V308P/N325G/M428I/N434Y F335 1.50E−08 S239K/M252Y/T256E/D270F/V308P/M428I/N434Y F336 1.40E−08 S239K/M252Y/D270F/T307Q/V308P/Q311A/ M428I/N434Y F337 5.60E−08 S239K/M252Y/D270F/T307Q/Q311A/M428I/N434Y F338 7.70E−09 S239K/M252Y/D270F/N286E/V308P/M428I/N434Y F339 1.90E−08 S239K/M252Y/D270F/V308P/L309E/M428I/N434Y F343 3.20E−08 S239K/M252Y/D270F/V308P/M428L/N434Y F344 3.00E−08 S239K/M252Y/V308P/M428L/N434Y F349 1.50E−07 S239K/M252Y/V308P/L309P/M428L/N434Y F350 1.70E−07 S239K/M252Y/V308P/L309R/M428L/N434Y F352 6.00E−07 S239K/M252Y/L309P/M428L/N434Y F353 1.10E−06 S239K/M252Y/L309R/M428L/N434Y F354 2.80E−08 S239K/M252Y/T307Q/V308P/M428L/N434Y F356 3.40E−08 S239K/M252Y/D270F/V308P/L309E/P387E/N434Y F357 1.60E−08 S239K/M252Y/T256E/D270F/V308P/N325G/ M428I/N434Y F358 1.00E−07 S239K/M252Y/T307Q/N434Y F359 4.20E−07 P257V/T307Q/M428I/N434Y F360 1.30E−06 P257V/T307Q/M428V/N434Y F362 5.40E−08 P257V/T307Q/N325G/M428L/N434Y F363 4.10E−08 P257V/T307Q/Q311A/M428L/N434Y F364 3.50E−08 P257V/T307Q/Q311A/N325G/M428L/N434Y

Table 13-6 is the continuation of Table 13-5.

TABLE 13-6 F365 5.10E−08 P257V/V305A/T307Q/M428L/N434Y F367 1.50E−08 S239K/M252Y/E258H/D270F/T307Q/V308P/Q311A/N434Y F368 2.00E−08 S239K/M252Y/D270F/V308P/N325G/E382A/M428I/N434Y F369 7.50E−08 M252Y/P257V/T307Q/M428I/N434Y F372 1.30E−08 S239K/M252W/V308P/M428Y/N434Y F373 1.10E−08 S239K/M252W/V308P/Q311A/M428Y/N434Y F374 1.20E−08 S239K/M252W/T256E/V308P/M428Y/N434Y F375 5.50E−09 S239K/M252W/N286E/V308P/M428Y/N434Y F376 9.60E−09 S239K/M252Y/T256E/D270F/N286E/V308P/N434Y F377 1.30E−07 S239K/M252W/T307P/M428Y/N434Y F379 9.00E−09 S239K/M252W/T256E/V308P/Q311A/M428Y/N434Y F380 5.60E−09 S239K/M252W/T256E/N286E/V308P/M428Y/N434Y F381 1.10E−07 P257V/T307A/Q311A/M428L/N434Y F382 8.70E−08 P257V/V305A/T307A/M428L/N434Y F386 3.20E−08 M252Y/V308P/L309E/N434Y F387 1.50E−07 M252Y/V308P/L309D/N434Y F388 7.00E−08 M252Y/V308P/L309A/N434Y F389 1.70E−08 M252W/V308P/L309E/M428Y/N434Y F390 6.80E−08 M252W/V308P/L309D/M428Y/N434Y F391 3.60E−08 M252W/V308P/L309A/M428Y/N434Y F392 6.90E−09 S239K/M252Y/N286E/V308P/M428I/N434Y F393 1.20E−08 S239K/M252Y/N286E/V308P/N434Y F394 5.30E−08 S239K/M252Y/T307Q/Q311A/M428I/N434Y F395 2.40E−08 S239K/M252Y/T256E/V308P/N434Y F396 2.00E−08 S239K/M252Y/D270F/N286E/T307Q/Q311A/M428I/N434Y F397 4.50E−08 S239K/M252Y/D270F/T307Q/Q311A/P387E/M428I/N434Y F398 4.40E−09 S239K/M252Y/D270F/N286E/T307Q/V308P/Q311A/M428I/N434Y F399 6.50E−09 S239K/M252Y/D270F/N286E/T307Q/V308P/M428I/N434Y F400 6.10E−09 S239K/M252Y/D270F/N286E/V308P/Q311A/M428I/N434Y F401 6.90E−09 S239K/M252Y/D270F/N286E/V308P/P387E/M428I/N434Y F402 2.30E−08 P257V/T307Q/M428L/N434W F403 5.10E−08 P257V/T307A/M428L/N434W F404 9.40E−08 P257A/T307Q/L309P/M428L/N434Y F405 1.70E−07 P257V/T307Q/L309P/M428L/N434Y F406 1.50E−07 P257A/T307Q/L309R/M428L/N434Y F407 1.60E−07 P257V/T307Q/L309R/M428L/N434Y F408 2.50E−07 P257V/N286E/M428L/N434Y F409 2.00E−07 P257V/P387E/M428L/N434Y F410 2.20E−07 P257V/T307H/M428L/N434Y F411 1.30E−07 P257V/T307N/M428L/N434Y F412 8.80E−08 P257V/T307G/M428L/N434Y F413 1.20E−07 P257V/T307P/M428L/N434Y F414 1.10E−07 P257V/T307S/M428L/N434Y F415 5.60E−08 P257V/N286E/T307A/M428L/N434Y F416 9.40E−08 P257V/T307A/P387E/M428L/N434Y F418 6.20E−07 S239K/M252Y/T307P/N325G/M428Y/N434Y F419 1.60E−07 M252Y/T307A/Q311H/K360H/N434Y F420 1.50E−07 M252Y/T307A/Q311H/P387E/N434Y F421 1.30E−07 M252Y/T307A/Q311H/M428A/N434Y F422 1.80E−07 M252Y/T307A/Q311H/E382A/N434Y F423 8.40E−08 M252Y/T307W/Q311H/N434Y F424 9.40E−08 S239K/P257A/V308P/M428L/N434Y F425 8.00E−08 P257A/V308P/L309E/M428L/N434Y F426 8.40E−08 P257V/T307Q/N434Y F427 1.10E−07 M252Y/P257V/T307Q/M428V/N434Y F428 8.00E−08 M252Y/P257V/T307Q/M428L/N434Y F429 3.70E−08 M252Y/P257V/T307Q/N434Y F430 8.10E−08 M252Y/P257V/T307Q/M428Y/N434Y F431 6.50E−08 M252Y/P257V/T307Q/M428F/N434Y F432 9.20E−07 P257V/T307Q/Q311A/N325G/M428V/N434Y

Table 13-7 is the continuation of Table 13-6.

TABLE 13-7 F433 6.00E−08 P257V/T307Q/Q311A/N325G/N434Y F434 2.00E−08 P257V/T307Q/Q311A/N325G/M428Y/N434Y F435 2.50E−08 P257V/T307Q/Q311A/N325G/M428F/N434Y F436 2.50E−07 P257A/T307Q/M428V/N434Y F437 5.70E−08 P257A/T307Q/N434Y F438 3.60E−08 P257A/T307Q/M428Y/N434Y F439 4.00E−08 P257A/T307Q/M428F/N434Y F440 1.50E−08 P257V/N286E/T307Q/Q311A/N325G/M428L/N434Y F441 1.80E−07 P257A/Q311A/M428L/N434Y F442 2.00E−07 P257A/Q311H/M428L/N434Y F443 5.50E−08 P257A/T307Q/Q311A/M428L/N434Y F444 1.40E−07 P257A/T307A/Q311A/M428L/N434Y F445 6.20E−08 P257A/T307Q/Q311H/M428L/N434Y F446 1.10E−07 P257A/T307A/Q311H/M428L/N434Y F447 1.40E−08 P257A/N286E/T307Q/M428L/N434Y F448 5.30E−08 P257A/N286E/T307A/M428L/N434Y F449 5.70E−07 S239K/M252Y/D270F/T307P/N325G/M428Y/N434Y F450 5.20E−07 S239K/M252Y/T307P/L309E/N325G/M428Y/N434Y F451 1.00E−07 P257S/T307A/M428L/N434Y F452 1.40E−07 P257M/T307A/M428L/N434Y F453 7.80E−08 P257N/T307A/M428L/N434Y F454 9.60E−08 P257I/T307A/M428L/N434Y F455 2.70E−08 P257V/T307Q/M428Y/N434Y F456 3.40E−08 P257V/T307Q/M428F/N434Y F457 4.00E−08 S239K/P257V/V308P/M428L/N434Y F458 1.50E−08 P257V/T307Q/V308P/N325G/M428L/N434Y F459 1.30E−08 P257V/T307Q/V308P/Q311A/N325G/M428L/N434Y F460 4.70E−08 P257V/T307A/V308P/N325G/M428L/N434Y F462 8.50E−08 P257A/V308P/N325G/M428L/N434Y F463 1.30E−07 P257A/T307A/V308P/M428L/N434Y F464 5.50E−08 P257A/T307Q/V308P/M428L/N434Y F465 2.10E−08 P257V/N286E/T307Q/N325G/M428L/N434Y F466 3.50E−07 T256E/P257V/N434Y F467 5.70E−07 T256E/P257T/N434Y F468 5.70E−08 S239K/P257T/V308P/M428L/N434Y F469 5.60E−08 P257T/V308P/N325G/M428L/N434Y F470 5.40E−08 T256E/P257T/V308P/N325G/M428L/N434Y F471 6.60E−08 P257T/V308P/N325G/E382A/M428L/N434Y F472 5.40E−08 P257T/V308P/N325G/P387E/M428L/N434Y F473 4.50E−07 P257T/V308P/L309P/N325G/M428L/N434Y F474 3.50E−07 P257T/V308P/L309R/N325G/M428L/N434Y F475 4.30E−08 T256E/P257V/T307Q/M428L/N434Y F476 5.50E−08 P257V/T307Q/E382A/M428L/N434Y F477 4.30E−08 P257V/T307Q/P387E/M428L/N434Y F480 3.90E−08 P257L/V308P/N434Y F481 5.60E−08 P257T/T307Q/N434Y F482 7.00E−08 P257V/T307Q/N325G/N434Y F483 5.70E−08 P257V/T307Q/Q311A/N434Y F484 6.20E−08 P257V/V305A/T307Q/N434Y F485 9.70E−08 P257V/N286E/T307A/N434Y F486 3.40E−07 P257V/T307Q/L309R/Q311H/M428L/N434Y F488 3.50E−08 P257V/V308P/N325G/M428L/N434Y F490 7.50E−08 S239K/P257V/V308P/Q311H/M428L/N434Y F492 9.80E−08 P257V/V305A/T307A/N325G/M428L/N434Y F493 4.90E−07 S239K/D270F/T307P/N325G/M428Y/N434Y F497 3.10E−06 P257T/T307A/M428V/N434Y F498 1.30E−06 P257A/M428V/N434Y F499 5.20E−07 P257A/T307A/M428V/N434Y F500 4.30E−08 P257S/T307Q/M428L/N434Y F506 1.90E−07 P257V/N297A/T307Q/M428L/N434Y

Table 13-8 is the continuation of Table 13-7.

TABLE 13-8 F507 5.10E−08 P257V/N286A/T307Q/M428L/N434Y F508 1.10E−07 P257V/T307Q/N315A/M428L/N434Y F509 5.80E−08 P257V/T307Q/N384A/M428L/N434Y F510 5.30E−08 P257V/T307Q/N389A/M428L/N434Y F511 4.20E−07 P257V/N434Y F512 5.80E−07 P257T/N434Y F517 3.10E−07 P257V/N286E/N434Y F518 4.20E−07 P257T/N286E/N434Y F519 2.60E−08 P257V/N286E/T307Q/N434Y F521 1.10E−08 P257V/N286E/T307Q/M428Y/N434Y F523 2.60E−08 P257V/V305A/T307Q/M428Y/N434Y F526 1.90E−08 P257T/T307Q/M428Y/N434Y F527 9.40E−09 P257V/T307Q/V308P/N325G/M428Y/N434Y F529 2.50E−08 P257T/T307Q/M428F/N434Y F533 1.20E−08 P257A/N286E/T307Q/M428F/N434Y F534 1.20E−08 P257A/N286E/T307Q/M428Y/N434Y F535 3.90E−08 T250A/P257V/T307Q/M428L/N434Y F538 9.90E−08 T250F/P257V/T307Q/M428L/N434Y F541 6.00E−08 T250I/P257V/T307Q/M428L/N434Y F544 3.10E−08 T250M/P257V/T307Q/M428L/N434Y F549 5.40E−08 T250S/P257V/T307Q/M428L/N434Y F550 5.90E−08 T250V/P257V/T307Q/M428L/N434Y F551 1.20E−07 T250W/P257V/T307Q/M428L/N434Y F552 1.10E−07 T250Y/P257V/T307Q/M428L/N434Y F553 1.70E−07 M252Y/Q311A/N434Y F554 2.80E−08 S239K/M252Y/S254T/V308P/N434Y F556 1.50E−06 M252Y/T307Q/Q311A F559 8.00E−08 M252Y/S254T/N286E/N434Y F560 2.80E−08 M252Y/S254T/V308P/N434Y F561 1.40E−07 M252Y/S254T/T307A/N434Y F562 8.30E−08 M252Y/S254T/T307Q/N434Y F563 1.30E−07 M252Y/S254T/Q311A/N434Y F564 1.90E−07 M252Y/S254T/Q311H/N434Y F565 9.20E−08 M252Y/S254T/T307A/Q311A/N434Y F566 6.10E−08 M252Y/S254T/T307Q/Q311A/N434Y F567 2.20E−07 M252Y/S254T/M428I/N434Y F568 1.10E−07 M252Y/T256E/T307A/Q311H/N434Y F569 2.00E−07 M252Y/T256Q/T307A/Q311H/N434Y F570 1.30E−07 M252Y/S254T/T307A/Q311H/N434Y F571 8.10E−08 M252Y/N286E/T307A/Q311H/N434Y F572 1.00E−07 M252Y/T307A/Q311H/M428I/N434Y F576 1.60E−06 M252Y/T256E/T307Q/Q311H F577 1.30E−06 M252Y/N286E/T307A/Q311A F578 5.70E−07 M252Y/N286E/T307Q/Q311A F580 8.60E−07 M252Y/N286E/T307Q/Q311H F581 7.20E−08 M252Y/T256E/N286E/N434Y F582 7.50E−07 S239K/M252Y/V308P F583 7.80E−07 S239K/M252Y/V308P/E382A F584 6.30E−07 S239K/M252Y/T256E/V308P F585 2.90E−07 S239K/M252Y/N286E/V308P F586 1.40E−07 S239K/M252Y/N286E/V308P/M428I F587 1.90E−07 M252Y/N286E/M428L/N434Y F592 2.00E−07 M252Y/S254T/E382A/N434Y F593 3.10E−08 S239K/M252Y/S254T/V308P/M428I/N434Y F594 1.60E−08 S239K/M252Y/T256E/V308P/M428I/N434Y F595 1.80E−07 S239K/M252Y/M428I/N434Y F596 4.00E−07 M252Y/D312A/E382A/M428Y/N434Y F597 2.20E−07 M252Y/E382A/P387E/N434Y F598 1.40E−07 M252Y/D312A/P387E/N434Y F599 5.20E−07 M252Y/P387E/M428Y/N434Y

Table 13-9 is the continuation of Table 13-8.

TABLE 13-9 F600 2.80E−07 M252Y/T256Q/E382A/N434Y F601 9.60E−09 M252Y/N286E/V308P/N434Y F608 G236A/S239D/I332E F611 2.80E−07 M252Y/V305T/T307P/V308I/L309A/N434Y F612 3.60E−07 M252Y/T307P/V308I/L309A/N434Y F613 S239D/A330L/I332E F616 S239D/K326D/L328Y F617 7.40E−07 S239K/N434W F618 6.40E−07 S239K/V308F/N434Y F619 3.10E−07 S239K/M252Y/N434Y F620 2.10E−07 S239K/M252Y/S254T/N434Y F621 1.50E−07 S239K/M252Y/T307A/Q311H/N434Y F622 3.50E−07 S239K/M252Y/T256Q/N434Y F623 1.80E−07 S239K/M252W/N434W F624 1.40E−08 S239K/P257A/N286E/T307Q/M428L/N434Y F625 7.60E−08 S239K/P257A/T307Q/M428L/N434Y F626 1.30E−06 V308P F629 3.90E−08 M252Y/V279L/V308P/N434Y F630 3.70E−08 S239K/M252Y/V279L/V308P/N434Y F633 2.40E−08 M252Y/V282D/V308P/N434Y F634 3.20E−08 S239K/M252Y/V282D/V308P/N434Y F635 4.50E−08 M252Y/V284K/V308P/N434Y F636 4.80E−08 S239K/M252Y/V284K/V308P/N434Y F637 1.50E−07 M252Y/K288S/V308P/N434Y F638 1.40E−07 S239K/M252Y/K288S/V308P/N434Y F639 2.70E−08 M252Y/V308P/G385R/N434Y F640 3.60E−08 S239K/M252Y/V308P/G385R/N434Y F641 3.00E−08 M252Y/V308P/Q386K/N434Y F642 3.00E−08 S239K/M252Y/V308P/Q386K/N434Y F643 3.20E−08 L235G/G236R/S239K/M252Y/V308P/N434Y F644 3.00E−08 G236R/S239K/M252Y/V308P/N434Y F645 3.30E−08 S239K/M252Y/V308P/L328R/N434Y F646 3.80E−08 S239K/M252Y/N297A/V308P/N434Y F647 2.90E−08 P238D/M252Y/V308P/N434Y F648 P238D F649 1.20E−07 S239K/M252Y/N286E/N434Y F650 1.70E−07 S239K/M252Y/T256E/N434Y F651 1.80E−07 S239K/M252Y/Q311A/N434Y F652 2.40E−07 P238D/M252Y/N434Y F654 3.20E−08 L235K/S239K/M252Y/V308P/N434Y F655 3.40E−08 L235R/S239K/M252Y/V308P/N434Y F656 3.30E−08 G237K/S239K/M252Y/V308P/N434Y F657 3.20E−08 G237R/S239K/M252Y/V308P/N434Y F658 3.20E−08 P238K/S239K/M252Y/V308P/N434Y F659 3.00E−08 P238R/S239K/M252Y/V308P/N434Y F660 3.10E−08 S239K/M252Y/V308P/P329K/N434Y F661 3.40E−08 S239K/M252Y/V308P/P329R/N434Y F663 6.40E−09 S239K/M252Y/N286E/T307Q/V308P/Q311A/N434Y F664 3.90E−08 M252Y/N286A/V308P/N434Y F665 2.00E−08 M252Y/N286D/V308P/N434Y F666 2.10E−08 M252Y/N286F/V308P/N434Y F667 3.00E−08 M252Y/N286G/V308P/N434Y F668 4.00E−08 M252Y/N286H/V308P/N434Y F669 3.50E−08 M252Y/N286I/V308P/N434Y F670 2.10E−07 M252Y/N286K/V308P/N434Y F671 2.20E−08 M252Y/N286L/V308P/N434Y F672 2.40E−08 M252Y/N286M/V308P/N434Y F673 2.30E−08 M252Y/N286P/V308P/N434Y F674 3.20E−08 M252Y/N286Q/V308P/N434Y F675 5.10E−08 M252Y/N286R/V308P/N434Y

Table 13-10 is the continuation of Table 13-9.

TABLE 13-10 F676 3.20E−08 M252Y/N286S/V308P/N434Y F677 4.70E−08 M252Y/N286T/V308P/N434Y F678 3.30E−08 M252Y/N286V/V308P/N434Y F679 1.70E−08 M252Y/N286W/V308P/N434Y F680 1.50E−08 M252Y/N286Y/V308P/N434Y F681 4.90E−08 M252Y/K288A/V308P/N434Y F682 8.20E−08 M252Y/K288D/V308P/N434Y F683 5.00E−08 M252Y/K288E/V308P/N434Y F684 5.10E−08 M252Y/K288F/V308P/N434Y F685 5.30E−08 M252Y/K288G/V308P/N434Y F686 4.60E−08 M252Y/K288H/V308P/N434Y F687 4.90E−08 M252Y/K288I/V308P/N434Y F688 2.80E−08 M252Y/K288L/V308P/N434Y F689 4.10E−08 M252Y/K288M/V308P/N434Y F690 1.00E−07 M252Y/K288N/V308P/N434Y F691 3.20E−07 M252Y/K288P/V308P/N434Y F692 3.90E−08 M252Y/K288Q/V308P/N434Y F693 3.60E−08 M252Y/K288R/V308P/N434Y F694 4.70E−08 M252Y/K288V/V308P/N434Y F695 4.00E−08 M252Y/K288W/V308P/N434Y F696 4.40E−08 M252Y/K288Y/V308P/N434Y F697 3.10E−08 S239K/M252Y/V308P/N325G/N434Y F698 2.20E−08 M252Y/N286E/T307Q/Q311A/N434Y F699 2.30E−08 S239K/M252Y/N286E/T307Q/Q311A/N434Y F700 5.20E−08 M252Y/V308P/L328E/N434Y F705 7.10E−09 M252Y/N286E/V308P/M428I/N434Y F706 1.80E−08 M252Y/N286E/T307Q/Q311A/M428I/N434Y F707 5.90E−09 M252Y/N286E/T307Q/V308P/Q311A/N434Y F708 4.10E−09 M252Y/N286E/T307Q/V308P/Q311A/M428I/N434Y F709 2.00E−08 S239K/M252Y/N286E/T307Q/Q311A/M428I/N434Y F710 1.50E−08 P238D/M252Y/N286E/T307Q/Q311A/M428I/N434Y F711 6.50E−08 S239K/M252Y/T307Q/Q311A/N434Y F712 6.00E−08 P238D/M252Y/T307Q/Q311A/N434Y F713 2.00E−08 P238D/M252Y/N286E/T307Q/Q311A/N434Y F714 2.30E−07 P238D/M252Y/N325S/N434Y F715 2.30E−07 P238D/M252Y/N325M/N434Y F716 2.70E−07 P238D/M252Y/N325L/N434Y F717 2.60E−07 P238D/M252Y/N325I/N434Y F718 2.80E−07 P238D/M252Y/Q295M/N434Y F719 7.40E−08 P238D/M252Y/N325G/N434Y F720 2.40E−08 M252Y/T307Q/V308P/Q311A/N434Y F721 1.50E−08 M252Y/T307Q/V308P/Q311A/M428I/N434Y F722 2.70E−07 P238D/M252Y/A327G/N434Y F723 2.80E−07 P238D/M252Y/L328D/N434Y F724 2.50E−07 P238D/M252Y/L328E/N434Y F725 4.20E−08 L235K/G237R/S239K/M252Y/V308P/N434Y F726 3.70E−08 L235K/P238K/S239K/M252Y/V308P/N434Y F729 9.20E−07 T307A/Q311A/N434Y F730 6.00E−07 T307Q/Q311A/N434Y F731 8.50E−07 T307A/Q311H/N434Y F732 6.80E−07 T307Q/Q311H/N434Y F733 3.20E−07 M252Y/L328E/N434Y F734 3.10E−07 G236D/M252Y/L328E/N434Y F736 3.10E−07 M252Y/S267M/L328E/N434Y F737 3.10E−07 M252Y/S267L/L328E/N434Y F738 3.50E−07 P238D/M252Y/T307P/N434Y F739 2.20E−07 M252Y/T307P/Q311A/N434Y F740 2.90E−07 M252Y/T307P/Q311H/N434Y F741 3.10E−07 P238D/T250A/M252Y/N434Y F744 9.90E−07 P238D/T250F/M252Y/N434Y

Table 13-11 is the continuation of Table 13-10.

TABLE 13-11 F745 6.60E−07 P238D/T250G/M252Y/N434Y F746 6.00E−07 P238D/T250H/M252Y/N434Y F747 2.80E−07 P238D/T250I/M252Y/N434Y F749 5.10E−07 P238D/T250L/M252Y/N434Y F750 3.00E−07 P238D/T250M/M252Y/N434Y F751 5.30E−07 P238D/T250N/M252Y/N434Y F753 1.80E−07 P238D/T250Q/M252Y/N434Y F755 3.50E−07 P238D/T250S/M252Y/N434Y F756 3.70E−07 P238D/T250V/M252Y/N434Y F757 1.20E−06 P238D/T250W/M252Y/N434Y F758 1.40E−06 P238D/T250Y/M252Y/N434Y F759 L235K/S239K F760 L235R/S239K F761 1.10E−06 P238D/N434Y F762 3.60E−08 L235K/S239K/M252Y/N286E/T307Q/Q311A/N434Y F763 3.50E−08 L235R/S239K/M252Y/N286E/T307Q/Q311A/N434Y F764 6.30E−07 P238D/T307Q/Q311A/N434Y F765 8.50E−08 P238D/M252Y/T307Q/L309E/Q311A/N434Y F766 6.00E−07 T307A/L309E/Q311A/N434Y F767 4.30E−07 T307Q/L309E/Q311A/N434Y F768 6.40E−07 T307A/L309E/Q311H/N434Y F769 4.60E−07 T307Q/L309E/Q311H/N434Y F770 3.00E−07 M252Y/T256A/N434Y F771 4.00E−07 M252Y/E272A/N434Y F772 3.80E−07 M252Y/K274A/N434Y F773 3.90E−07 M252Y/V282A/N434Y F774 4.00E−07 M252Y/N286A/N434Y F775 6.20E−07 M252Y/K338A/N434Y F776 3.90E−07 M252Y/K340A/N434Y F777 3.90E−07 M252Y/E345A/N434Y F779 3.90E−07 M252Y/N361A/N434Y F780 3.90E−07 M252Y/Q362A/N434Y F781 3.70E−07 M252Y/S375A/N434Y F782 3.50E−07 M252Y/Y391A/N434Y F783 4.00E−07 M252Y/D413A/N434Y F784 5.00E−07 M252Y/L309A/N434Y F785 7.40E−07 M252Y/L309H/N434Y F786 2.80E−08 M252Y/S254T/N286E/T307Q/Q311A/N434Y F787 8.80E−08 M252Y/S254T/T307Q/L309E/Q311A/N434Y F788 4.10E−07 M252Y/N315A/N434Y F789 1.50E−07 M252Y/N315D/N434Y F790 2.70E−07 M252Y/N315E/N434Y F791 4.40E−07 M252Y/N315F/N434Y F792 4.40E−07 M252Y/N315G/N434Y F793 3.30E−07 M252Y/N315I/N434Y F794 4.10E−07 M252Y/N315K/N434Y F795 3.10E−07 M252Y/N315L/N434Y F796 3.40E−07 M252Y/N315M/N434Y F798 3.50E−07 M252Y/N315Q/N434Y F799 4.10E−07 M252Y/N315R/N434Y F800 3.80E−07 M252Y/N315S/N434Y F801 4.40E−07 M252Y/N315T/N434Y F802 3.30E−07 M252Y/N315V/N434Y F803 3.60E−07 M252Y/N315W/N434Y F804 4.00E−07 M252Y/N315Y/N434Y F805 3.00E−07 M252Y/N325A/N434Y F806 3.10E−07 M252Y/N384A/N434Y F807 3.20E−07 M252Y/N389A/N434Y F808 3.20E−07 M252Y/N389A/N390A/N434Y F809 2.20E−07 M252Y/S254T/T256S/N434Y

Table 13-12 is the continuation of Table 13-11.

TABLE 13-12 F810 2.20E−07 M252Y/A378V/N434Y F811 4.90E−07 M252Y/E380S/N434Y F812 2.70E−07 M252Y/E382V/N434Y F813 2.80E−07 M252Y/S424E/N434Y F814 1.20E−07 M252Y/N434Y/Y436I F815 5.50E−07 M252Y/N434Y/T437R F816 3.80E−07 P238D/T250V/M252Y/T307P/N434Y F817 9.80E−08 P238D/T250V/M252Y/T307Q/Q311A/N434Y F819 1.40E−07 P238D/M252Y/N286E/N434Y F820 3.40E−07 L235K/S239K/M252Y/N434Y F821 3.10E−07 L235R/S239K/M252Y/N434Y F822 1.10E−06 P238D/T250Y/M252Y/W313Y/N434Y F823 1.10E−06 P238D/T250Y/M252Y/W313F/N434Y F828 2.50E−06 P238D/T250V/M252Y/I253V/N434Y F831 1.60E−06 P238D/T250V/M252Y/R255A/N434Y F832 2.60E−06 P238D/T250V/M252Y/R255D/N434Y F833 8.00E−07 P238D/T250V/M252Y/R255E/N434Y F834 8.10E−07 P238D/T250V/M252Y/R255F/N434Y F836 5.00E−07 P238D/T250V/M252Y/R255H/N434Y F837 5.60E−07 P238D/T250V/M252Y/R255I/N434Y F838 4.30E−07 P238D/T250V/M252Y/R255K/N434Y F839 3.40E−07 P238D/T250V/M252Y/R255L/N434Y F840 4.20E−07 P238D/T250V/M252Y/R255M/N434Y F841 1.10E−06 P238D/T250V/M252Y/R255N/N434Y F843 6.60E−07 P238D/T250V/M252Y/R255Q/N434Y F844 1.30E−06 P238D/T250V/M252Y/R255S/N434Y F847 3.40E−07 P238D/T250V/M252Y/R255W/N434Y F848 8.30E−07 P238D/T250V/M252Y/R255Y/N434Y F849 3.30E−07 M252Y/D280A/N434Y F850 2.90E−07 M252Y/D280E/N434Y F852 3.30E−07 M252Y/D280G/N434Y F853 3.20E−07 M252Y/D280H/N434Y F855 3.20E−07 M252Y/D280K/N434Y F858 3.20E−07 M252Y/D280N/N434Y F860 3.30E−07 M252Y/D280Q/N434Y F861 3.20E−07 M252Y/D280R/N434Y F862 3.00E−07 M252Y/D280S/N434Y F863 2.70E−07 M252Y/D280T/N434Y F867 2.80E−07 M252Y/N384A/N389A/N434Y F868 2.00E−08 G236A/S239D/M252Y/N286E/T307Q/Q311A/N434Y F869 G236A/S239D F870 7.30E−08 L235K/S239K/M252Y/T307Q/Q311A/N434Y F871 7.10E−08 L235R/S239K/M252Y/T307Q/Q311A/N434Y F872 1.30E−07 L235K/S239K/M252Y/N286E/N434Y F873 1.20E−07 L235R/S239K/M252Y/N286E/N434Y F875 4.80E−07 M252Y/N434Y/Y436A F877 8.30E−07 M252Y/N434Y/Y436E F878 1.90E−07 M252Y/N434Y/Y436F F879 9.20E−07 M252Y/N434Y/Y436G F880 3.90E−07 M252Y/N434Y/Y436H F881 3.10E−07 M252Y/N434Y/Y436K F882 1.30E−07 M252Y/N434Y/Y436L F883 2.10E−07 M252Y/N434Y/Y436M F884 4.00E−07 M252Y/N434Y/Y436N F888 4.80E−07 M252Y/N434Y/Y436S F889 2.20E−07 M252Y/N434Y/Y436T F890 1.10E−07 M252Y/N434Y/Y436V F891 1.70E−07 M252Y/N434Y/Y436W F892 7.10E−08 M252Y/S254T/N434Y/Y436I F893 9.80E−08 L235K/S239K/M252Y/N434Y/Y436I

Table 13-13 is the continuation of Table 13-12.

TABLE 13-13 F894 9.20E−08 L235R/S239K/M252Y/N434Y/Y436I F895 2.10E−08 L235K/S239K/M252Y/N286E/T307Q/Q311A/ N315E/N434Y F896 2.00E−08 L235R/S239K/M252Y/N286E/T307Q/Q311A/ N315E/N434Y F897 9.70E−08 M252Y/N315D/N384A/N389A/N434Y F898 1.70E−07 M252Y/N315E/N384A/N389A/N434Y F899 1.10E−07 M252Y/N315D/G316A/N434Y F900 1.70E−07 M252Y/N315D/G316D/N434Y F901 1.30E−07 M252Y/N315D/G316E/N434Y F902 2.20E−07 M252Y/N315D/G316F/N434Y F903 2.30E−07 M252Y/N315D/G316H/N434Y F904 1.00E−07 M252Y/N315D/G316I/N434Y F905 1.30E−07 M252Y/N315D/G316K/N434Y F906 1.50E−07 M252Y/N315D/G316L/N434Y F907 1.30E−07 M252Y/N315D/G316M/N434Y F908 1.50E−07 M252Y/N315D/G316N/N434Y F909 1.30E−07 M252Y/N315D/G316P/N434v F910 1.40E−07 M252Y/N315D/G316Q/N434Y F911 1.30E−07 M252Y/N315D/G316R/N434Y F912 1.20E−07 M252Y/N315D/G316S/N434Y F913 1.10E−07 M252Y/N315D/G316T/N434Y F914 1.50E−07 M252Y/N315D/G316V/N434Y F915 2.30E−07 M252Y/N315D/G316W/N434Y F917 2.50E−07 M252Y/N286S/N434Y F918 2.80E−07 M252Y/D280E/N384A/N389A/N434Y F919 3.30E−07 M252Y/D280G/N384A/N389A/N434Y F920 2.50E−07 M252Y/N286S/N384A/N389A/N434Y F921 1.20E−07 M252Y/N286E/N384A/N389A/N434Y F922 5.90E−08 L235K/S239K/M252Y/N286E/N434Y/Y436I F923 6.00E−08 L235R/S239K/M252Y/N286E/N434Y/Y436I F924 3.40E−08 L235K/S239K/M252Y/T307Q/Q311A/N434Y/Y436I F925 3.20E−08 L235R/S239K/M252Y/T307Q/Q311A/N434Y/Y436I F926 1.10E−07 L235K/S239K/M252Y/S254T/N434Y/Y436I F927 1.00E−07 L235R/S239K/M252Y/S254T/N434Y/Y436I F928 2.90E−08 M252Y/T307Q/Q311A/N434Y/Y436I F929 2.90E−08 M252Y/S254T/T307Q/Q311A/N434Y/Y436I F930 1.40E−07 P238D/T250V/M252Y/N286E/N434Y F931 1.20E−07 P238D/T250V/M252Y/N434Y/Y436I F932 3.20E−07 T250V/M252Y/N434Y F933 3.00E−07 L234R/P238D/M250V/M252Y/N434Y F934 3.10E−07 G236K/P238D/T250V/M252Y/N434Y F935 3.20E−07 G237K/P238D/T250V/M252Y/N434Y F936 3.20E−07 G237R/P238D/T250V/M252Y/N434Y F937 3.10E−07 P238D/S239K/T250V/M252Y/N434Y F938 1.60E−07 L235K/S239K/M252Y/N434Y/Y436V F939 1.50E−07 L235R/S239K/M252Y/N434Y/Y436V F940 1.50E−07 P238D/T250V/M252Y/N434Y/Y436V F941 1.20E−08 M252Y/N286E/T307Q/Q311A/N434Y/Y436V F942 4.20E−08 L235K/S239K/M252Y/T307Q/Q311A/N434Y/Y436V F943 4.00E−08 L235R/S239K/M252Y/T307Q/Q311A/N434Y/Y436V F944 1.70E−07 T250V/M252Y/N434Y/Y436V F945 1.70E−08 T250V/M252Y/V308P/N434Y/Y436V F946 4.30E−08 T250V/M252Y/T307Q/Q311A/N434Y/Y436V F947 1.10E−08 T250V/M252Y/T307Q/V308P/Q311A/N434Y/Y436V F954 5.30E−07 M252Y/N434Y/H435K/Y436V F957 7.70E−07 M252Y/N434Y/H435N/Y436V F960 8.00E−07 M252Y/N434Y/H435R/Y436V F966 3.10E−07 M252Y/S254A/N434Y F970 2.50E−06 M252Y/S254G/N434Y F971 2.60E−06 M252Y/S254H/N434Y F972 2.60E−07 M252Y/S254I/N434Y

Table 13-14 is the continuation of Table 13-13.

TABLE 13-14 F978 1.30E−06 M252Y/S254Q/N434Y F980 1.80E−07 M252Y/S254V/N434Y F987 4.00E−08 P238D/T250V/M252Y/T307Q/Q311A/N434Y/Y436V F988 6.90E−08 P238D/T250V/M252Y/N286E/N434Y/Y436V F989 1.40E−08 L235R/S239K/M252Y/V308P/N434Y/Y436V F990 9.40E−09 L235R/S239K/M252Y/T307Q/V308P/Q311A/N434Y/Y436V F991 1.30E−08 L235R/S239K/M252Y/N286E/T307Q/Q311A/N434Y/Y436V F992 5.10E−08 L235R/S239K/M252Y/T307Q/Q311A/M428I/N434Y/Y436V F993 3.80E−08 M252Y/T307Q/Q311A/N434Y/Y436V F994 2.80E−07 M252Y/N325G/N434Y F995 2.90E−07 L235R/P238D/S239K/M252Y/N434Y F996 1.30E−07 L235R/P238D/S239K/M252Y/N434Y/Y436V F997 3.80E−07 K248I/T250V/M252Y/N434Y/Y436V F998 8.50E−07 K248Y/T250V/M252Y/N434Y/Y436V F999 2.10E−07 T250V/M252Y/E258H/N434Y/Y436V F1005 N325G F1008 1.70E−07 L235R/S239K/T250V/M252Y/N434Y/Y436V F1009 1.20E−08 L235R/S239K/T250V/M252Y/T307Q/V308P/Q311A/N434Y/Y436V F1010 1.90E−07 L235R/S239K/M252Y/T307A/Q311H/N434Y F1011 4.50E−08 T250V/M252Y/V308P/N434Y F1012 4.70E−08 L235R/S239K/T250V/M252Y/V308P/N434Y F1013 3.00E−08 T250V/M252Y/T307Q/V308P/Q311A/N434Y F1014 3.20E−08 L235R/S239K/T250V/M252Y/T307Q/V308P/Q311A/N434Y F1015 2.20E−08 L235R/S239K/M252Y/T307Q/V308P/Q311A/N434Y F1016 3.80E−09 T250V/M252Y/N286E/T307Q/V308P/Q311A/N434Y/Y436V F1017 4.20E−09 L235R/S239K/T250V/M252Y/N286E/T307Q/V308P/Q311A/N434Y/Y436V F1018 3.20E−09 L235R/S239K/M252Y/N286E/T307Q/V308P/Q311A/N434Y/Y436V F1019 3.40E−07 P238D/T250V/M252Y/N325G/N434Y F1020 8.50E−08 P238D/T250V/M252Y/T307Q/Q311A/N325G/N434Y F1021 3.30E−07 P238D/T250V/M252Y/N325A/N434Y F1022 K326D/L328Y F1023 4.40E−08 S239D/T250V/M252Y/T307Q/Q311A/N434Y/Y436V F1024 4.00E−08 T250V/M252Y/T307Q/Q311A/K326D/L328Y/N434Y/Y436V F1025 3.60E−08 S239D/T250V/M252Y/T307Q/Q311A/K326D/L328Y/N434Y/Y436V F1026 8.40E−08 M252Y/T307A/Q311H/N434Y/Y436V F1027 8.60E−08 L235R/S239K/M252Y/T307A/Q311H/N434Y/Y436V F1028 4.60E−08 G236A/S239D/T250V/M252Y/T307Q/Q311A/N434Y/Y436V F1029 5.10E−08 T250V/M252Y/T307Q/Q311A/I332E/N434Y/Y436V F1030 I332E F1031 5.30E−08 G236A/S239D/T250V/M252Y/T307Q/Q311A/I332E/N434Y/Y436V F1032 4.30E−08 P238D/T250V/M252Y/T307Q/Q311A/N325G/N434Y/Y436V F1033 1.00E−06 P238D/N434W F1034 1.50E−08 L235K/S239K/M252Y/V308P/N434Y/Y436V F1035 1.00E−08 L235K/S239K/M252Y/T307Q/V308P/Q311A/N434Y/Y436V F1036 1.40E−08 L235K/S239K/M252Y/N286E/T307Q/Q311A/N434Y/Y436V F1037 6.10E−08 L235K/S239K/M252Y/T307Q/Q311A/M428I/N434Y/Y436V F1038 2.80E−07 L235K/P238D/S239K/M252Y/N434Y F1039 1.30E−07 L235K/P238D/S239K/M252Y/N434Y/Y436V F1040 2.00E−07 L235K/S239K/T250V/M252Y/N434Y/Y436V F1041 1.40E−08 L235K/S239K/T250V/M252Y/T307Q/V308P/Q311A/N434Y/Y436V F1042 2.00E−07 L235K/S239K/M252Y/T307A/Q311H/N434Y F1043 5.20E−08 L235K/S239K/T250V/M252Y/V308P/N434Y F1044 3.50E−08 L235K/S239K/T250V/M252Y/T307Q/V308P/Q311A/N434Y F1045 2.50E−08 L235K/S239K/M252Y/T307Q/V308P/Q311A/N434Y F1046 4.50E−09 L235K/S239K/T250V/M252Y/N286E/T307Q/V308P/Q311A/N434Y/Y436V F1047 3.40E−09 L235K/S239K/M252Y/N286E/T307Q/V308P/Q311A/N434Y/Y436V F1048 9.90E−08 L235K/S239K/M252Y/T307A/Q311H/N434Y/Y436V F1050 3.50E−09 T250V/M252Y/N286E/T307Q/V308P/Q311A/M428I/N434Y/Y436V F1051 3.90E−09 L235R/S239K/T250V/M252Y/N286E/T307Q/V308P/Q311A/M428I/N434Y/Y436V F1052 3.20E−09 L235R/S239K/M252Y/N286E/T307Q/V308P/Q311A/M428I/N434Y/Y436V

Reference Example 1 Construction of Antibody Expression Vectors; and Expression and Purification of Antibodies

Synthesis of full-length genes encoding the nucleotide sequences of the H chain and L chain of the antibody variable regions was carried out by production methods known to those skilled in the art using Assemble PCR and such. Introduction of amino acid substitutions was carried out by methods known to those skilled in the art using PCR or such. The obtained plasmid fragment was inserted into an animal cell expression vector, and the H-chain expression vector and L-chain expression vector were produced. The nucleotide sequence of the obtained expression vector was determined by methods known to those skilled in the art. The produced plasmids were introduced transiently into the HEK293H cell line derived from human embryonic kidney cancer cells (Invitrogen) or into FreeStyle293 cells (Invitrogen) for antibody expression. The obtained culture supernatant was collected, and then passed through a 0.22 μm MILLEX®-GV filter (Millipore), or through a 0.45 μm MILLEX®-GV filter (Millipore) to obtain the culture supernatant. Antibodies were purified from the obtained culture supernatant by methods known to those skilled in the art using rProtein A Sepharose Fast Flow (GE Healthcare) or Protein G Sepharose 4 Fast Flow (GE Healthcare). For the concentration of the purified antibodies, their absorbance at 280 nm was measured using a spectrophotometer. From the obtained value, the extinction coefficient calculated by the methods such as PACE was used to calculate the antibody concentration (Protein Science 1995; 4: 2411-2423).

Reference Example 2 Method for Preparing FcγR and Method for Analyzing the Interaction Between an Altered Antibody and FcγR

Extracellular domains of FcγRs were prepared by the following method. First, a gene of the extracellular domain of FcγR was synthesized by a method well known to those skilled in the art. At that time, the sequence of each FcγR was produced based on the information registered at NCBI. Specifically, FcγRI was produced based on the sequence of NCBI Accession No. NM_000566 (Version No. NM_000566.3), FcγRIIa was produced based on the sequence of NCBI Accession No. NM_001136219 (Version No. NM_001136219.1), FcγRIIb was produced based on the sequence of NCBI Accession No. NM_004001 (Version No. NM_004001.3), FcγRIIIa was produced based on the sequence of NCBI Accession No. NM_001127593 (Version No. NM_001127593.1), and FcγRIIIb was produced based on the sequence of NCBI Accession No. NM_000570 (Version No. NM_000570.3), and a His tag was attached to the C terminus. Furthermore, the presence of polymorphism is known for FcγRIIa, FcγRIIIa, and FcγRIIIb, and the polymorphic sites were produced by referring to Warmerdam et al. (J. Exp. Med., 1990, 172; 19-25) for FcγRIIa; Wu et al. (J. Clin. Invest., 1997, 100 (5): 1059-1070) for FcγRIIIa; and Ory et al. (J. Clin. Invest., 1989, 84, 1688-1691) for FcγRIIIb.

The obtained gene fragments were inserted into an animal cell expression vector, and expression vectors were produced. The produced expression vectors were introduced transiently into human embryonic kidney cancer cell-derived FreeStyle293 cells (Invitrogen) to express the proteins of interest. Regarding FcγRIIb used for crystal structure analysis, the protein of interest was expressed in the presence of Kifunesine at a final concentration of 10 μg/mL, so that the sugar chain added to FcγRIIb will be the high-mannose type. Cells were cultured, and after collection of the obtained culture supernatant, this was passed through a 0.22 μm filter to obtain the culture supernatant. In principle, the obtained culture supernatants were purified in the following four steps. The steps carried out were, cation exchange column chromatography (SP Sepharose FF) in step 1, affinity column chromatography (HisTrap HP) for His tag in step 2, gel filtration column chromatography (Superdex200) in step 3, and aseptic filtration in step 4. However, for FcγRI, anion exchange column chromatography using Q sepharose FF was performed as step 1. The purified proteins were subjected to absorbance measurements at 280 nm using a spectrophotometer; and from the obtained values, the concentrations of the purified proteins were calculated using the absorption coefficient calculated using methods such as PACE (Protein Science 1995; 4: 2411-2423).

Analysis of interaction between each altered antibody and the Fcγ receptor prepared as mentioned above was carried out using Biacore T100 (GE Healthcare), Biacore T200 (GE Healthcare), Biacore A100, and Biacore 4000. HBS-EP+ (GE Healthcare) was used as the running buffer, and the measurement temperature was set to 25° C. Chips produced by immobilizing the antigen peptide, Protein A (Thermo Scientific), Protein A/G (Thermo Scientific), and Protein L (ACTIGEN or BioVision) by the amine coupling method to a Series S sensor Chip CM5 (GE Healthcare) or Series S sensor Chip CM4 (GE Healthcare), or alternatively, chips produced by allowing preliminarily biotinylated antigen peptides to interact with and immobilize onto a Series S Sensor Chip SA (certified) (GE Healthcare) were used.

After capturing of antibodies of interest onto these sensor chips, an Fcγ receptor diluted with the running buffer was allowed to interact, the amount bound to an antibody was measured, and compared among the antibodies. However, since the amount of Fcγ receptor bound depends on the amount of the captured antibodies, the amount of Fcγ receptor bound was divided by the amount of each antibody captured to obtain corrected values, and these values were compared. Furthermore, antibodies captured onto the sensor chips were washed by reaction with 10 mM glycine-HCl, pH 1.5, and the chips were regenerated and used repeatedly.

Kinetic analyses for calculating the KD values of each altered antibody for FcγR were performed according to the following method. First, antibodies of interest were captured onto the above-mentioned sensor chips, and an Fcγ receptor diluted with the running buffer was allowed to interact. The Biacore Evaluation Software was used to globally fit the measured results regarding the obtained sensorgram using the 1:1 Langmuir binding model, and the association rate constant ka (L/mol/s) and the dissociation rate constant kd (l/s) were calculated; and from those values the dissociation constants KD (mol/L) were calculated.

When the interaction between each of the altered antibodies and FcγR was weak, and correct analysis was determined to be impossible by the above-mentioned kinetic analysis, the KD for such interactions were calculated using the following 1:1 binding model equation described in the Biacore T100 Software Handbook BR1006-48 Edition AE.

The behavior of interacting molecules according to the 1:1 binding model on Biacore can be described by Equation 1 shown below.

R _(eq) =C·R _(max)/(KD+C)+RI  [Equation 1]

Req: a plot of steady state binding levels against analyte concentration C: concentration RI: bulk refractive index contribution in the sample Rmax: analyte binding capacity of the surface

When this equation is rearranged, KD can be expressed as Equation 2 shown below.

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

KD can be calculated by substituting the values of Rmax, RI, and C into this equation. The values of RI and C can be determined from the sensorgram of the measurement results and measurement conditions. Rmax was calculated according to the following method. As a target of comparison, for antibodies that had sufficiently strong interactions as evaluated simultaneously in the same round of measurement, the Rmax value was obtained through global fitting using the 1:1 Langmuir binding model, and then it was divided by the amount of the comparison antibody captured onto the sensor chip, and multiplied by the captured amount of an altered antibody to be evaluated.

Reference Example 3 Preparation of Soluble Human IL-6 Receptor (hsIL-6R)

Recombinant human IL-6 receptor which is an antigen was prepared in the manner described below. A CHO line that constantly expresses soluble human IL-6 receptor composed of an amino acid sequence consisting of the 1st to 357th amino acid from the N terminus as reported in J. Immunol. (1994) 152, 4958-4968 (hereinafter referred to as hsIL-6R) was constructed using a method known among persons with ordinary skill in the art. hsIL-6R was expressed by culturing this CHO line. hsIL-6R was purified from culture supernatant of the resulting CHO line by the two steps of Blue Sepharose 6 FF column chromatography and gel filtration column chromatography. The fraction that eluted as the main peak in the final step was used as the final purified product.

Reference Example 4 Elimination of Target Antigen from Plasma by pH-Dependent Binding Antibody Having Human FcRn-Binding Activity Under a Neutral pH Range Condition

When a conventional neutralizing antibody against a soluble antigen is administered, the plasma retention of the antigen is expected to be prolonged by binding to the antibody. In general, antibodies have a long half-life (one week to three weeks) while the half-life of antigen is generally short (one day or less). Meanwhile, antibody-bound antigens have a significantly longer half-life in plasma as compared to when the antigens are present alone. For this reason, administration of existing neutralizing antibody results in an increased antigen concentration in plasma. Such cases have been reported with various neutralizing antibodies that target soluble antigens including, for example, IL-6 (J Immunotoxicol. 2005, 3: 131-9), amyloid beta (mAbs, 2010, 2: 5, 1-13), MCP-1 (ARTHRITIS & RHEUMATISM 2006, 54: 2387-92), hepcidin (AAPS J. 2010, 4, 646-57), and sIL-6 receptor (Blood. 2008 November 15; 112(10): 3959-64). Administration of existing neutralizing antibodies has been reported to increase the total plasma antigen concentration to about 10 to 1000 times (the level of increase varies depending on antigen) from the base line. Herein, the total plasma antigen concentration refers to a concentration as a total amount of antigen present in plasma, i.e., the sum of concentrations of antibody-bound and antibody-unbound antigens. An increase in the total plasma antigen concentration is undesirable for such antibody pharmaceuticals that target a soluble antigen. The reason is that the plasma antibody concentration has to be higher than at least the total plasma antigen concentration to neutralize the soluble antigen. Specifically, “the total plasma antigen concentration is increased to 10 to 1.000 times” means that, in order to neutralize the antigen, the plasma antibody concentration (i.e., antibody dose) has to be 10 to 1,000 times higher as compared to when increase in the total plasma antigen concentration does not occur. Conversely, if the total plasma antigen concentration can be reduced by 10 to 1,000 times as compared to the existing neutralizing antibody, the antibody dose can also be reduced to similar extent. Thus, antibodies capable of decreasing the total plasma antigen concentration by eliminating the soluble antigen from plasma are highly useful as compared to existing neutralizing antibodies.

The examination described in PCT/JP2011/001888 demonstrated that antigen-binding molecules (IL-6 receptor-binding antibodies) with enhanced FcRn binding at pH 7.4 can reduce the total antigen concentration in plasma by eliminating the soluble antigen, and the effect to eliminate the soluble antigen is improved by conferring the property of binding to the antigen in a pH-dependent manner (binding to the antigen at pH 7.4 in plasma and dissociating from the antigen at pH 6.0 in the endosome). To reduce the total antigen concentration in plasma by administering an antigen-binding molecule, it is desirable that the antigen-binding molecule comprises an antigen-binding domain and a human FcRn-binding domain, and the human FcRn-binding domain has human FcRn binding activity under an acidic condition and under a neutral condition, and the human FcRn binding activity is 3200 nM or greater under a neutral condition. In this case, a control antigen-binding molecule has the same antigen-binding domain, and its human FcRn-binding domain is a native human IgG Fc region.

FIG. 9 shows a mechanism in which soluble antigens are eliminated from plasma by administering a pH-dependent antigen-binding antibody that has increased FcRn-binding activity at neutral pH as compared to a conventional neutralizing antibody. After binding to the soluble antigen in plasma, the existing neutralizing antibody that does not have the pH-dependent antigen-binding ability is slowly incorporated into cells by non-specific interaction with the cells. The complex between the neutralizing antibody and soluble antigen incorporated into the cell is transferred to the acidic endosome and then recycled to plasma by FcRn. Meanwhile, the pH-dependent antigen-binding antibody that has the increased FcRn-binding activity under the neutral condition is, after binding to the soluble antigen in plasma, rapidly incorporated into cells expressing FcRn on their cell membrane. Then, the soluble antigen bound to the pH-dependent antigen-binding antibody is dissociated from the antibody in the acidic endosome due to the pH-dependent binding ability. The soluble antigen dissociated from the antibody is transferred to the lysosome and degraded by proteolytic activity. Meanwhile, the antibody dissociated from the soluble antigen is recycled onto cell membrane by FcRn and then released to plasma again. The free antibody, recycled as described above, can again bind to other soluble antigens. By repeating such cycle: FcRn-mediated uptake into cells; dissociation and degradation of the soluble antigen; and antibody recycling, such pH-dependent antigen-binding antibodies as described above having the increased FcRn binding activity under the neutral condition can transfer a large amount of soluble antigen to the lysosome and thereby decrease the total antigen concentration in plasma.

Reference Example 5 Demonstration of the In Vivo Pharmaceutical Effect of an Antibody without Neutralizing Activity In Vitro by Eliminating Target Antigens from Plasma

It has been believed that, to exhibit the in vivo pharmaceutical effect to neutralize target antigens, antigen-binding molecules must have an in vitro activity of neutralizing the target antigens. The reason is that, if ordinary antigen-binding molecules do not have in vitro neutralizing activity, they cannot exhibit the in vivo pharmaceutical effect by neutralizing target antigens.

Meanwhile, Reference Example 4 shows that, when administered in vivo, pH-dependent binding antibodies that have human FcRn-binding activity under a neutral pH range condition can eliminate target antigens from plasma. The present inventors conceived that, if a target antigen was eliminated from plasma by administering an antibody, the action of the target antigen can be substantially blocked even when the antibody does not have antigen-neutralizing activity.

Isolation of the pH-Dependent Antibody 6RKE02-IgG1 Against Human IL-6 Receptor from Human Naive Library

A human antibody phage display library consisting of multiple phages that display Fab domains of different human antibody sequences was constructed according to a method known to those skilled in the art using as a template poly A RNA prepared from human PBMCs or commercially-available human poly A RNA.

The first selection from the constructed naive human antibody phage display library was performed by enriching only antibody fragments with antigen-binding ability. A biotin-labeled human IL-6 receptor was used as an antigen.

Phages were produced by E. coli containing the constructed phage display phagemids. To precipitate the phages, 2.5 M NaCl/10% PEG was added to the E. coli culture media of phage production. The phages were diluted with TBS to prepare a phage library solution. Then, BSA and CaCl₂ were added at a final concentration of 4% BSA and a final calcium ion concentration of 1.2 mM respectively to the phage library solution. Regarding the panning method, the present inventors referred to general panning methods using antigens immobilized onto magnetic beads (J. Immunol. Methods. (2008) 332 (1-2), 2-9, J. Immunol. Methods. (2001) 247 (1-2), 191-203, Biotechnol. Prog. (2002) 18(2) 212-20, Mol. Cell Proteomics (2003) 2 (2), 61-9). The magnetic beads used were NeutrAvidin coated beads (Sera-Mag SpeedBeads NeutrAvidin-coated) and Streptavidin coated beads (Dynabeads M-280 Streptavidin).

Specifically, 250 μmol of biotin-labeled antigen was added to the prepared phage library solution to contact it with the phage library solution at room temperature for 60 minutes. BSA-blocked magnetic beads were added thereto and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed once with 1 ml of 1.2 mM CaCl₂/TBS (TBS containing 1.2 mM CaCl₂). Then, a phage solution was collected according to a general method. The collected phage solution was added to 10 ml of E. coli strain TG1 in the logarithmic growth phase (OD600 of 0.4-0.5). The E. coli was infected with the phages by culturing them while gently stirring at 37° C. for one hour. The infected E. coli was seeded in a 225 mm×225 mm plate. Then, the phages were collected from the culture medium of the seeded E. coli to prepare a phage library solution.

To enrich the phages, the second and subsequent pannings were performed using the pH-dependent binding ability as an indicator. Specifically, 40 pmol of the biotin-labeled antigen was added to the prepared phage library solution, and contacted it with the phage library at room temperature for 60 minutes. BSA-blocked magnetic beads were added thereto and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed with 1 ml of 1.2 mM CaCl₂/TBST (TBS containing 1.2 mM CaCl₂ and 0.1% Tween 20) and with 1.2 mM CaCl₂/TBS. Then, the beads combined with 0.1 ml of 50 mM MES/1.2 mM CaCl₂/150 mM NaCl (pH 5.5) were suspended at room temperature, and immediately separated using a magnetic stand to collect a phage solution. The collected phage solution was added to 10 ml of E. coli strain TG1 in the logarithmic growth phase (OD600 of 0.4-0.5). The E. coli was infected with the phages by culturing them while gently stirring at 37° C. for one hour. The infected E. coli was seeded in a 225 mm×225 mm plate. Then, the phages were collected from the culture medium of the seeded E. coli to prepare a phage library solution. The panning using the pH-dependent binding ability as an indicator was performed repeatedly several times.

After repeating the panning twice, three times, or four times, phage-containing culture supernatants were collected according to a conventional method (Methods Mol. Biol. (2002) 178, 133-145) from single colonies of E. coli obtained by the method described above.

To the phage-containing culture supernatants, BSA and CaCl₂ were added at a final concentration of 4% BSA and at a final calcium ion concentration of 1.2 mM, respectively. The phage-containing culture supernatants were subjected to ELISA by the following procedure. A StreptaWell 96 microtiter plate (Roche) was coated overnight with 100 μl of PBS containing the biotin-labeled antigen. After washing each well of the plate with PBST to remove the antigen, the wells were blocked with 250 μl of 4% BSA/TBS for one hour or more. After removing 4% BSA/TBS from the wells, the culture supernatants prepared as mentioned above were added thereto. The antibodies presented on the phages were allowed to bind to the antigens on each well by incubating the plate at 37° C. for one hour. The wells were washed with 1.2 mM CaCl₂/TBST, and 1.2 mM CaCl₂/TBS (pH 7.6) or 1.2 mM CaCl₂/TBS (pH 5.5) was added thereto. The plate was incubated by being allowed to stand at 37° C. for 30 minutes. After washing with 1.2 mM CaCl₂/TBST (pH 7.6), an HRP-linked anti-M13 antibody (Amersham Pharmacia Biotech) diluted with TBS containing BSA at a final concentration of 4% and ionized calcium at a final concentration of 1.2 mM was added to each well. The plate was incubated for one hour. After washing with 1.2 mM CaCl₂/TBST, TMB single solution (ZYMED) was added thereto. The chromogenic reaction in the solution of each well was stopped by adding sulfuric acid, and then the absorbance at 450 nm was measured to assess the color development.

Furthermore, the genes amplified with specific primers using as a template the clones subjected to phage ELISA were analyzed for their nucleotide sequence.

Based on the results of the above-mentioned phage ELISA and sequence analysis, selection was performed using pooled libraries containing many antibody fragments which were considered to have the ability to bind to the antigen in a pH-dependent manner.

Expression of Antibodies

Antibody genes from pooled libraries containing many clones that were considered to have the ability to bind to the antigen in a pH-dependent manner based on the result of phage ELISA, were inserted into animal cell expression plasmids. Antibody expression was carried out using the method described below. The FreeStyle 293-F line (Invitrogen) derived from human fetal kidney cells were suspended in FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 2.63×10⁵ cells/ml in 190 μl to each well of a 96-well plate. The prepared plasmids were introduced into the cells by a lipofection method. The cells were cultured in a CO₂ incubator (37° C., 8% CO₂) for four days.

Analysis and Assessment of Interaction Using Biacore A100

Antibodies isolated by the above-described method were analyzed using Biacore A100 (GE Healthcare) for the interaction between IL-6R and the antibodies of interest. The running buffer used was: 10 mM ACES, 150 mM NaCl, 1.2 mM CaCl₂, 0.05% Tween20, pH 7.4, or 10 mM ACES, 150 mM NaCl, 1.2 mM CaCl₂, 0.05% Tween20, pH 6.0. The measurement temperature was 25° C. The chip used was a Series S Sencor Chip CM5 (GE Healthcare) immobilized with Protein A/G (Thermo Scientific) by an amine coupling method. Antibodies of interest were captured onto the chip, and allowed to interact with IL-6R diluted with the running buffer. The antibodies captured onto the chip were washed off by reacting 10 mM glycine-HCl (pH 1.5), and the chip was regenerated for repeated use.

The IL-6R-binding activity of each antibody was assessed mainly using as an indicator the binding amount of IL-6R to the antibody. The amount of change (RU) in sensorgram upon interaction of the captured antibody with IL-6R, divided by the amount of change (RU) upon capturing the antibody onto the chip, was used as the binding amount of IL-6R to the antibody.

Expression and Purification of Antibodies

Clones that were determined to have the ability to bind to the antigen in a pH-dependent manner, based on the result of screening with BiacoreA100, were expressed again to perform the assessment. Antibodies were prepared using the method described in Reference Example 1.

Assessment of 6RKE02-IgG1 for its pH-Dependent Binding to Soluble Human IL-6 Receptor

The above method yielded 6RKE02-IgG1 having 6RKE02H-IgG1 (SEQ ID NO: 1) as the heavy chain and 6RKE02L-k0 (SEQ ID NO: 2) as the light chain. 6RKE02-IgG1 was analyzed for its interaction with IL-6R using Biacore T100 (GE Healthcare), and the dissociation constant (KD) was calculated.

The running buffer used was 10 mM ACES (pH 7.4) containing 150 mM NaCl and 0.05% Tween20. The measurement temperature was 37° C. The chip used was a Series S Sencor Chip CM4 (GE Healthcare) immobilized with Protein A/G (Thermo Scientific) by an amine coupling method. Antibodies of interest were captured onto the chip, and allowed to interact with IL-6R diluted with the running buffer to 800, 400, 200, 100, 50, 25, and 12.5 nM, and the running buffer at a flow rate of 2 μl/minute for 15 minutes. The antibodies captured onto the chip were washed off by reacting 10 mM glycine-HCl (pH 1.5), and the chip was regenerated for repeated use.

From the sensorgrams obtained as a result of the Biacore measurement, the dissociation constant KD (mol/l) of 6RKE02-IgG1 for IL-6R was calculated by performing steady state affinity analysis using Biacore Evaluation Software. The dissociation constant (KD) between 6RKE02-IgG1 and IL-6R at pH 7.4, calculated by this method, was 1.4E-7 (M).

Next, the pH dependence of the binding of 6RKE02-IgG1 to hIL-6R was assessed using Biacore T100. The running buffer used was: 10 mM ACES, 150 mM NaCl, 0.05% Tween20, pH 7.4; and 10 mM ACES, 150 mM NaCl, 0.05% Tween20, pH 6.0. The measurement temperature was 37° C. The chip used was a Series S Sencor Chip CM4 (GE Healthcare) immobilized with Protein A/G (Thermo Scientific) by an amine coupling method. Antibodies of interest were captured onto the chip, and allowed to interact with hIL-6R diluted with the running buffer to 1000, 250, and 62.5 nM, and the running buffer.

Sensorgrams obtained by the measurement at pH 7.4 and pH 6.0 using this method are shown in FIG. 10. The captured amount of antibody has been normalized to be 100 RU, and the binding phase and dissociation phase of 6RKE02-IgG1 for hIL-6R are shown. A comparison of the results shown in FIG. 10 revealed that the binding of 6REK02-IgG1 to hIl-6R was reduced at pH 6.0 as compared to pH 7.4.

Assessment for Biological Activity Using BaF3 Cells Expressing Human gp130 (BaF/gp130)

6RKE02-IgG1 and Tocilizumab were assessed for their IL-6 receptor-neutralizing activity using BaF3/gp130 that shows human IL-6/soluble human IL-6 receptor-dependent growth. After washing three times with RPMI1640 medium containing 10% FBS, BaF3/gp130 was suspended in RPMI1640 medium containing 10% FBS and prepared at 1.5×10⁵ cells/ml with a final concentration of 15 ng/ml for both human interleukin-6 (R&D Systems) and soluble human IL-6 receptor. This was aliquoted at 50 μl to each well of a 96 well-plate (CORNING). Then, the purified antibodies were serially diluted with PBS, and then diluted 20 times with RPMI1640 medium containing 10% FBS, and added at 50 μl to each well. The cells were cultured at 37° C. under 5% CO₂ for three days, and WST-8 reagent (Cell Counting Kit-8, DOJINDO LABORATORIES) diluted twice with PBS was added thereto at 20 μl/well. After four hours of incubation, the absorbance at 450 nm (reference wavelength of 620 nm) was measured with microplate reader xMark (Bio-Rad Laboratories) to assess the IL-6 receptor-neutralizing activity. The result is shown in FIG. 11. 6RKE02-IgG1 did not inhibit the human IL-6/soluble human IL-6 receptor-dependent growth of BaF3/gp130. Thus, it was shown that 6RKE02-IgG1 does not have the neutralizing activity.

Preparation of 6RKE02-IgG1 with Increased FcRn-Binding Activity in a Neutral pH Range

To confer the mouse FcRn-binding activity under a neutral pH range condition to 6RKE02-IgG1, amino acid mutations were introduced into 6RKE02H-IgG1, which is the heavy chain constant region of 6RKE02-IgG1. Specifically, 6RKE02H-F29 (SEQ ID NO: 3) was constructed by introducing into 6RKE02H-IgG1 an amino acid substitution of Val for Ile at position 332 (EU numbering) and an amino acid substitution of Tyr for Asn at position 434 (EU numbering), using the method described in Reference Example 1. 6RKE02-F29, which contains 6RKE02H-F29 as the heavy chain and 6RKE02L-k0 as the light chain, was constructed using the method described in Reference Example 1.

Kinetic Analysis for the Binding to Mouse FcRn

VH3/L(WT)-IgG1 comprising VH3-IgG1 (SEQ ID NO: 4) and L(WT)-CK (SEQ ID NO: 5), and VH3/L(WT)-F29 comprising VH3-F29 (SEQ ID NO: 6) and L(WT)-CK (SEQ ID NO: 5) were constructed to assess the mouse FcRn-binding activity of 6RKE02-F29.

Using VH3/L(WT)-IgG1 and VH3/L(WT)-F29, the mouse FcRn-binding activity was assessed as follows.

Mouse FcRn and antibodies were kinetically analyzed using Biacore T100 (GE Healthcare). An appropriate amount of protein L (ACTIGEN) was immobilized onto a Sensor chip CM4 (GE Healthcare) by an amine coupling method, and antibodies of interest were captured onto the chip. Then, a diluted mouse FcRn solution and a running buffer as a blank were injected, and mouse FcRn was allowed to interact with the antibodies captured onto the sensor chip. The running buffer used was 50 mmol/l sodium phosphate, 150 mmol/l NaCl, 0.05% (w/v) Tween20, pH 7.0. The buffer was also used to dilute mouse FcRn. 10 mmol/l glycine-HCl (pH 1.5) was used for regeneration. All measurements were carried out at 25° C. The binding rate constant ka (l/Ms) and dissociation rate constant kd (Us), which are kinetic parameters, were calculated from the sensorgrams obtained by the measurement, and the KD (M) of each antibody for mouse FcRn was calculated based on the values. Each parameter was calculated using Biacore T100 or T200 Evaluation Software (GE Healthcare).

The result is shown in Table 14 (KD of human IgG1 or F29 for mouse FcRn). F29 was demonstrated to have increased mouse FcRn-binding activity under a neutral pH range condition (pH 7.0).

TABLE 14 ANTIBODY mFcRn KD (M) AMINO ACID SUBSTITUTION HUMAN IgG1 ND F29 8.5E−08 I332V/N434Y

In Vivo Infusion Test Using Normal Mouse

An infusion pump (MODEL2004, alzet MINI-OSMOTIC PUMP), filled with soluble human IL-6 receptor, was subcutaneously implanted into the back of a normal mouse (C57BL/6J mouse, Charles River Japan) to create an animal model with plasma concentration of soluble human IL-6 receptor maintained in the steady state. In the animal model, the anti-human IL-6 receptor antibody was administered to assess the in vivo kinetics of soluble human IL-6 receptor after antibody administration. To suppress the production of neutralizing antibodies against soluble human IL-6 receptor, an anti-mouse CD4 monoclonal antibody (in-house preparation) was administered once at 20 mg/kg into the tail vein. Then, an infusion pump containing 92.8 μg/ml soluble human IL-6 receptor was implanted subcutaneously on the back of mice. Three days after implantation of the infusion pump, 6RKE02-IgG1 and 6RKE02-F29 were administered once at 1 mg/kg subcutaneously on the back of the normal mice. Blood was collected at appropriate time points after administration of the anti-human IL-6 receptor antibody. The blood samples obtained were immediately centrifuged at 15,000 rpm for 15 minutes at 4° C. to separate plasma. The separated plasma was stored in a freezer set to −20° C. or lower until the time of measurement.

hsIL-6R concentration in mouse plasma was determined using electrochemiluminescence method. An hsIL-6R calibration curve sample prepared at 2,000, 1,000, 500, 250, 125, 62.5, or 31.25 μg/mL, and a mouse plasma measurement sample diluted by 50-fold or above, were mixed with a monoclonal anti-human IL-6R antibody (R&D) ruthenated with SULFO-TAG NHS Ester (Meso Scale Discovery), a biotinylated anti-human IL-6R antibody (R&D), and tocilizumab, followed by overnight reaction at 37° C. Tocilizumab was prepared at a final concentration of 333 μg/mL. Subsequently, the reaction solution was dispensed into an MA400 PR Streptavidin Plate (Meso Scale Discovery). In addition, after washing off the reaction solution that was allowed to react at room temperature for 1 hour, Read Buffer T (×4) (Meso Scale Discovery) was dispensed. Subsequently, the reaction solution was immediately subjected to measurement using a SECTOR PR 400 Reader (Meso Scale Discovery). The concentration of hsIL-6R was calculated from the response of the calibration curve using the SOFTmax PRO analysis software (Molecular Devices).

The time course of the monitored human IL-6 receptor concentration is shown in FIG. 12. The plasma hsIL-6R concentration was not reduced in the antibody non-administered group and the 6RKE02-IgG1 administered group. By contrast, the plasma hsIL-6R concentration was found to be markedly reduced in the group administered with 6RKE02-F29 that binds to the IL-6 receptor in a pH-dependent manner and has the activity of binding mouse FcRn in a neutral range.

In Vivo Drug Efficacy Test Using Normal Mice (Test 1)

Whether 6RKE02-F29 that has no neutralizing activity in vitro can achieve the in vivo pharmaceutical effect by eliminating hsIL-6R from the plasma was assessed by using a normal mice model (C57BL/6J Jcl mice). It is known that, when a mixed solution of hIL-6 and hsIL-6R is administered to mice, the following two kinds of signaling are triggered: trans-signaling by the binding of hIL-6/hsIL-6R complexes to mouse gp130; and classical-signaling by the binding of hIL-6 to mouse membrane IL-6R followed by binding to mouse gp130; thus, the production of serum amyloid A (SAA) is induced, resulting in an increase of the plasma SAA concentration.

6RKE02-F29 was intravenously administered at 0, 1, 10, and 30 mg/kg to C57BL/6J Jcl mice (female), and, one hour after administration, hIL-6 and hsIL-6R were intravenously administered at 4 μg/kg and 7 μg/kg, respectively, as a mixture. Six hours after the second intravenous administration, blood was collected to determine the plasma SAA concentration by ELISA. To rule out the effect of endogenous mouse IL-6R on the plasma SAA concentration, MR16-1 (rat anti-mouse IL-6R antibody) was intravenously administered at 20 mg/kg to all mice simultaneously with the test substance. Since the trans-signaling alone is induced by administering hIL-6/hsIL-6R, it is possible to assess whether the in vivo pharmaceutical effect can be achieved through eliminating hsIL-6R from the plasma. Exclusion of the effect of endogenous mouse IL-6R was confirmed by intravenously administering hIL-6 at 4 μg/kg to the vehicle-administered group that was intravenously administered with MR16-1 at 20 mg/kg.

The plasma SAA concentration was measured using the SAA Mouse ELISA Kit (catalog NO. KMA0021, Life Technologies Corporation) according to the protocol attached to the kit. The plasma SAA concentration six hours after antibody administration is shown in FIG. 13. Meanwhile, the plasma hsIL-6R concentration six hours after antibody administration is shown in Table 15.

TABLE 15 samples ng/mL 6RKE02-F29 (F29) 30 mg/kg N.D. 6RKE02-F29 (F29) 10 mg/kg 0.38 6RKE02-F29 (F29) 1 mg/kg 3.22 IL6/IL6R 17.35 IL6 N.D.

It was confirmed that 6RKE02-F29 reduced the plasma hsIL-6R concentration in a dose-dependent manner and thus had the effect to reduce the plasma SAA concentration.

In Vivo Drug Efficacy Test Using Normal Mice (Test 2)

6RKE02-F29 was intravenously administered at 0, 10, and 30 mg/kg to C57BL/6J Jcl mice (female). In test 2, 24 hours after administration, hIL-6 and hsIL-6R were intravenously administered at 4 μg/kg and 7 μg/kg, respectively, as a mixture. Six hours after the second intravenous administration, the blood was collected to determine the plasma SAA concentration by ELISA. To rule out the effect of endogenous mouse IL-6R on the plasma SAA concentration, MR16-1 (rat anti-mouse IL-6R antibody) was intravenously administered at 20 mg/kg to all mice simultaneously with the test substance. Exclusion of the effect of endogenous mouse IL-6R was confirmed by intravenously administering hIL-6 at 4 μg/kg to the vehicle-administered group that was intravenously administered with MR16-1 at 20 mg/kg.

The plasma SAA concentration six hours after antibody administration is shown in FIG. 14. Meanwhile, the plasma hsIL-6R concentration six hours after antibody administration is shown in Table 16.

TABLE 16 samples ng/mL 6RKE02-F29 (F29) 30 mg/kg 0.22 6RKE02-F29 (F29) 10 mg/kg 0.82 IL6/IL6R 27.50 IL6 N.D.

It was confirmed that 6RKE02-F29 reduced the plasma hsIL-6R concentration in a dose-dependent manner and thus had the effect to reduce the plasma SAA concentration.

Tests 1 and 2 revealed that, although 6RKE02-F29 does not have in vitro inhibitory activity against the hsIL-6R-mediated trans-signaling, it can exhibit the in vivo inhibitory effect against the trans-signaling by eliminating hsIL-6R from the plasma.

Based on this finding, it can be said that, when using an antibody that binds to a target antigen in a pH-dependent manner and which has FcRn-binding activity in a neutral pH range, even if the antibody does not have the neutralizing activity to a specific epitope in vitro, the in vivo pharmaceutical effect (inhibitory effect) can be exhibited by eliminating the target antigen from the plasma Ordinary antigen-binding molecules including monoclonal antibodies can only bind to a single epitope. Meanwhile, in certain antigens, there are several antigenic sites to be neutralized; ordinary monoclonal antibodies can neutralize the action of a single epitope, but cannot neutralize the action of other epitopes of such antigens. Even in this case, as shown in this Example, the action of all epitopes can be substantially inhibited when eliminating the antigen from the plasma by using a monoclonal antibody that binds to the target antigen in a pH-dependent manner and which has FcRn-binding activity in a neural pH range.

Reference Example 6 Preparation of Antigen-Binding Molecules Whose Mouse FcγR-Binding Activity Under a Neutral pH Range Condition is Higher than the Binding Activity of Native Human IgG Fc Region

(6-1) pH-Dependent Human IL-6 Receptor-Binding Antibodies

H54/L28-IgG1 which comprises H54-IgG1 (SEQ ID NO: 113) and L28-CK (SEQ ID NO: 114) described in WO2009/125825 is a humanized anti-IL-6 receptor antibody. Meanwhile, Fv4-IgG1 which comprises VH3-IgG1 (SEQ ID NO: 4) and VL3-CK (SEQ ID NO: 122) is a humanized anti-IL-6 receptor antibody resulting from conferring, to H54/L28-IgG1, the property of binding to soluble human IL-6 receptor in a pH-dependent manner (which binds at pH 7.4 and dissociates at pH 5.8). The in vivo mouse test described in WO2009/125825 demonstrated that, in the group administered with a mixture of Fv4-IgG1 and soluble human IL-6 receptor as the antigen, the elimination of soluble human IL-6 receptor from plasma was significantly accelerated as compared to the group administered with a mixture of H54/L28-IgG1 and soluble human IL-6 receptor as the antigen.

The soluble human IL-6 receptor bound to H54/L28-IgG1 is, together with the antibody, recycled to plasma by FcRn. Meanwhile, Fv4-IgG1 dissociates soluble human IL-6 receptor under the acidic condition in the endosome, and the dissociated soluble human IL-6 receptor is degraded in the lysosomes, thus this enables considerable acceleration of the elimination of soluble human IL-6 receptor. After binding to FcRn in the endosome, Fv4-IgG1 is recycled to the plasma. Since the recycled antibody can bind to soluble human IL-6 receptor again, the antibody repeatedly binds to the antigen (soluble human IL-6 receptor) and is recycled by FcRn to the plasma. It is thought that, as a result, a single antibody molecule can bind repeatedly several times to soluble human IL-6 receptor (FIG. 15).

(6-2) Preparation of an Anti-Human IL-6 Receptor Antibody with Enhanced Mouse FcγR Binding and Anti-Human IL-6 Receptor Antibody without Mouse FcγR Binding

VH3-IgG1-F1022 (SEQ ID NO: 124), an antigen-binding molecule with enhanced mouse FcγR binding, was prepared by substituting Asp for Lys at position 326 (EU numbering) and Tyr for Leu at position 328 (EU numbering) in VH3-IgG1. Fv4-IgG1-F1022 containing VH3-IgG1-F1022 as the heavy chain and VL3-CK as the light chain was produced using the method described in Reference Example 1.

Meanwhile, VH3-IgG1-F760 (SEQ ID NO: 123), an antigen-binding molecule without mouse FcγR binding, was prepared by substituting Arg for Leu at position 235 and Lys for Ser at position 239 (EU numbering) in VH3-IgG1. Fv4-IgG1-F760 containing VH3-IgG1-F760 as the heavy chain and VL3-CK as the light chain was produced using the method described in Reference Example 1.

(6-3) Assessment of Mouse FcγR-Binding Activity

VH3/L(WT)-IgG1, VH3/L(WT)-IgG1-F1022, and VH3/L(WT)-IgG1-F760, which contain VH3-IgG1, VH3-IgG1-F1022, and VH3-IgG1-F760 as the heavy chain, respectively, and L(WT)-CK (SEQ ID NO: 5) as the light chain, were produced using the method described in Reference Example a. These antibodies were kinetically analyzed for their mouse FcγR binding as described below.

(6-4) Kinetic Analysis of Mouse FcγR Binding

The binding of antibodies to mouse FcγRI, FcγRIIb, FcγRIII, and FcγRIV (hereinafter, referred to as mouse FcγRs) (R&D systems, Sino Biological, or prepared by the method described in Reference Example 2) was kinetically analyzed using Biacore T100 and T200 (GE Healthcare). An appropriate amount of protein L (ACTIGEN or BioVision) was immobilized onto a Sensor chip CM4 (GE Healthcare) by an amine coupling method, and antibodies of interest were captured thereto. Then, diluted solutions of mouse FcγRs and a running buffer as a blank were injected, and the mouse FcγRs were allowed to interact with antibodies captured onto the sensor chip. The running buffer used was 20 mmol/l ACES, 150 mmol/l NaCl, 0.05% (w/v) Tween20, pH 7.4. This buffer was also used to dilute the mouse FcγRs. The sensor chip was regenerated using 10 mmol/l glycine-HCl, pH 1.5. All measurements were carried out at 25° C. The binding rate constant ka (1/Ms) and dissociation rate constant kd (1/s), which are kinetic parameters, were calculated from the sensorgrams obtained by the measurement. KD (M) of each antibody for human FcγR was calculated based on the values. Each parameter was calculated using Biacore T100 or T200 Evaluation Software (GE Healthcare).

The result shown in Table 17 was obtained by the measurement. VH3/L (WT)-IgG1-F1022 was demonstrated to have increased binding activity to mFcγRI, mFcγRIIb, and mFcγRIII as compared to VH3/L (WT)-IgG1. Regarding VH3/L (WT)-IgG1-F760, the binding to the various mouse FcγRs was undetectable, demonstrating that VH3/L (WT)-IgG1-F760 lacks the binding activity to the various mouse FcγRs. In the table, VH3/L (WT)-IgG1 is abbreviated as IgG1; VH3/L (WT)-IgG1-F1022 is abbreviated as F1022; and VH3/L (WT)-IgG1-F760 is abbreviated as F760.

TABLE 17 VARIANT KD (M) NAME mFcγRI mFcγRII mFcγRIIII mFcγRIV IgG1 5.3E−08 9.8E−07 2.4E−06 8.6E−08 F1022 7.6E−09 1.0E−08 5.5E−09 1.4E−07 F760 NOT NOT NOT NOT DETECTED DETECTED DETECTED DETECTED (6-5) Preparation of Antibodies with Low Fucose Content

Known methods for increasing the FcγR-binding activity of antibodies include methods for making sugar chains linked to an antibody be sugar chains with low fucose content (J. Biol. Chem. (2003) 278, 3466-3473) in addition to methods for introducing an amino acid alteration into the Fc region of an antibody. An Fv4-IgG1 with low fucose content (hereinafter, abbreviated as Fv4-IgG1-Fuc) was produced by expressing Fv4-IgG1 using fucose transporter gene-deficient CHO cells (WO2006/067913) as host cells according to the method described in Reference Example 1. It has been reported that, of the mFcγRs (mouse Fcγ receptors), antibodies with low fucose content have selectively increased FcγRIV-binding activity (Science, 2005, 310 (5753) 1510-1512).

Reference Example 7 Effect of Eliminating Antigens from Plasma by Antigen-Binding Molecules Whose FcγR-Binding Activity is Higher than the Binding Activity of Native Human IgG Fc Region

(7-1) Effect of H54/L28-IgG1 and Fv4-IgG1 to Eliminate Antigens from Plasma

H54/L28-IgG1, which is an anti-human IL-6 receptor antibody, and Fv4-IgG1 having the property of binding to human IL-6 receptor in a pH-dependent manner were produced by the method described in Reference Example 1. In vivo infusion tests were carried out using the produced H54/L28-IgG1 and Fv4-IgG1 by the method described below.

(7-1-1) In Vivo Infusion Tests Using Human FcRn Transgenic Mice

An animal model in which the soluble human IL-6 receptor concentration is maintained constant in plasma was created by implanting an infusion pump (MINI-OSMOTIC PUMP MODEL2004, alzet) containing soluble human IL-6 receptor under the skin on the back of human FcRn transgenic mice (B6.mFcRn−/−.hFcRn Tg line 32+/+ mouse. Jackson Laboratories, Methods Mol Biol. (2010) 602, 93-104). The in vivo dynamics after administration of an anti-human IL-6 receptor antibody was assessed in the animal model. To suppress the production of neutralizing antibodies against soluble human IL-6 receptor, an anti-mouse CD4 monoclonal antibody (prepared by a known method) was administered once at 20 mg/kg into the tail vein. Then, an infusion pump containing 92.8 μg/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice. Three days after implantation of the infusion pump, an anti-human IL-6 receptor antibody was administered once at 1 mg/kg into the tail vein. The blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, and seven days after administration of the anti-human IL-6 receptor antibody. Immediately, the collected blood was centrifuged at 15.000 rpm and 4° C. for 15 minutes to prepare plasma. The isolated plasma was stored in a freezer set at −20° C. or below until use.

(7-1-2) Determination of the Soluble Human IL-6 Receptor (hsIL-6R) Concentration in Plasma by an Electrochemiluminescent Method

The hsIL-6R concentrations in mouse plasma were determined by an electrochemiluminescent method. hsIL-6R standard curve samples prepared at 2000, 1000, 500, 250, 125, 62.5, and 31.25 μg/ml and assay samples of mouse plasma diluted 50 times or more were mixed with Monoclonal Anti-human IL-6R Antibody (R&D) which had been ruthenated with SULFO-TAG NHS Ester (Meso Scale Discovery), Biotinylated Anti-human IL-6 R Antibody (R&D), and Tocilizumab. The mixtures were incubated at 37° C. overnight. Tocilizumab was prepared at a final concentration of 333 μg/ml. Then, the reaction mixtures were aliquoted in an MA400 PR Streptavidin Plate (Meso Scale Discovery). The solution reacted at room temperature for one hour was washed out, and then Read Buffer T (×4) (Meso Scale Discovery) was aliquoted. Immediately thereafter, the measurement was carried out using SECTOR PR 400 Reader (Meso Scale Discovery). The concentration of hsIL-6R was determined based on the response of the standard curve using analysis software SOFTmax PRO (Molecular Devices).

A time course of the monitored human IL-6 receptor concentration is shown in FIG. 16. As compared to H54/L28-IgG1, Fv4-IgG1 that binds to human IL-6 receptor in a pH-dependent manner could reduce the human IL-6 receptor concentration, but could not reduce it below the baseline without antibody administration. That is, the administered antibody which binds to an antigen in a pH-dependent manner could not reduce the antigen concentration in plasma below the level prior to antibody administration.

(7-2) The Effect of Eliminating an Antigen from Plasma by an Antibody with Increased or Reduced FcγR-Binding Activity

Whether the time course of human IL-6 receptor concentration is influenced by increasing or reducing the FcγR-binding activity of Fv4-IgG1, which is a pH-dependent human IL-6 receptor-binding antibody, was assessed by the method described below. Using Fv4-IgG1, Fv4-IgG1-F760, Fv4-IgG1-F1022, and Fv4-IgG1-Fuc prepared as described in Reference Example 6, in vivo infusion tests were performed by the method described below.

(7-2-1) In Vivo Infusion Tests Using Human FcRn Transgenic Mice

A animal model in which the soluble human IL-6 receptor concentration is maintained constant in plasma was created by implanting an infusion pump (MINI-OSMOTIC PUMP MODEL2004, alzet) containing soluble human IL-6 receptor under the skin on the back of human FcRn transgenic mice (B6.mFcRn−/−.hFcRn Tg line 32+/+ mouse, Jackson Laboratories, Methods Mol Biol. (2010) 602, 93-104). In the animal model, an anti-human IL-6 receptor antibody was administered simultaneously with Sanglopor (CSL Behring) which is a human immunoglobulin preparation, to assess the in vivo dynamics of the soluble human IL-6 receptor after antibody administration. To suppress the production of neutralizing antibodies against soluble human IL-6 receptor, an anti-mouse CD4 monoclonal antibody (prepared by a known method) was administered once at 20 mg/kg into the tail vein. Then, an infusion pump containing 92.8 μg/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice. Three days after implantation of the infusion pump, an anti-human IL-6 receptor antibody and Sanglopor were administered once at 1 mg/kg and 1000 mg/kg, respectively, into the tail vein. The blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, seven days, 14 days, and 21 days after administration of the anti-human IL-6 receptor antibody. The blood was collected from the mice 15 minutes, seven hours, one day, two days, three days, seven days, 14 days, and 21 days after administration of the anti-human IL-6 receptor antibody. Immediately, the collected blood was centrifuged at 15,000 rpm and 4° C. for 15 minutes to prepare the plasma. The isolated plasma was stored in a freezer set at −20° C. or below until use.

(7-2-2) Determination of the Soluble Human IL-6 Receptor (hsIL-6R) Concentration in Plasma by an Electrochemiluminescent Method

The hsIL-6R concentrations in mouse plasma were determined by the same electrochemiluminescent method as described in (7-1-2).

The result is shown in FIG. 17. The time course of human IL-6 receptor concentration in plasma of mice administered with Fv4-IgG1-F760, from which the mouse FcγR binding of Fv4-IgG1 is deleted, was demonstrated to be comparable to that in mice administered with Fv4-IgG1. The cytotoxic activity to a membrane antigen depends on the FcγR binding, and thus the cytotoxic activity is lost when eliminating the FcγR binding. On the other hand, even when administering an antibody, from which mouse FcγR binding is deleted, against human IL-6 receptor which is a soluble antigen, there was no effect on the time course of human IL-6 receptor concentration in the plasma of the administered mice. Thus, it would be thought that the FcγR binding of an antibody against the soluble antigen has no contribution to the time course of antigen concentration in the plasma of mice administered with the antibody.

Surprisingly, however, the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1-F1022 with enhanced mouse FcγR binding was considerably reduced as compared to the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1. As to the degree of reduction, the concentration was confirmed to be decreased below the base-line human IL-6 receptor concentration without antibody administration. In particular, the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1-F1022 was reduced down to about 1/100 three days after administration as compared to the case of Fv4-IgG1 administration. This finding demonstrates that, by administering to mice an antibody that binds to human IL-6 receptor in a pH-dependent manner and whose FcγR binding has been enhanced, the human IL-6 receptor concentration in the plasma of the mice can be significantly reduced, and as to the degree of reduction, the antigen concentration in plasma can be reduced below the level before antibody administration.

Furthermore, it was also demonstrated that, as compared to mice administered with Fv4-IgG1, the human IL-6 receptor concentration in plasma was reduced in mice administered with Fv4-IgG I-Fuc which has sugar chains with low fucose content and with increased mouse FcγR IV-binding activity. In particular, the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG I-Fuc was reduced down to about ½ seven days after administration as compared to the case of Fv4-IgG1 administration. The above finding demonstrates that, by administering to mice a pH-dependent antigen-binding molecule that binds to human IL-6 receptor in a pH-dependent manner and whose FcγR binding has been enhanced, the soluble antigen concentration in the plasma of the mice can be reduced. Methods for enhancing the FcγR binding are not particularly limited to introduction of amino acid alterations. It was demonstrated that such enhancement can be achieved, for example, by using a human IgG Fc region to which a sugar chain with low fucose content is linked at position 297 (EU numbering), however, the effect of Fv4-IgG1-Fuc to reduce antigen concentration was smaller than Fv4-F1022. Thus, it would be thought that, of several FcγRs (FcγRI, II, III, and IV for mouse), mFcγIV, to which the binding of Fv4-IgG1-Fuc is enhanced, does not have a large contribution to the reduction of antigen concentration as an FcγR.

Thus, it was revealed that, by administering to an individual an antibody that binds to a soluble antigen in a pH-dependent manner and whose FcγR binding has been enhanced, the soluble antigen concentration in the plasma of the individual can be markedly reduced.

Without being bound by a particular theory, the unexpected reduction of soluble antigen concentration in plasma, which was observed when administering an antigen-binding molecule whose FcγR binding has been enhanced and that comprises an antigen-binding domain whose antigen-binding activity is altered depending on the ion concentration condition such as pH and an FcRn-binding domain that has FcRn-binding activity under an acidic pH range condition, can be explained as follows.

IgG antibodies that are non-specifically incorporated into cells return to the cell surface by binding to FcRn under the acidic condition in the endosome, and then dissociate from FcRn under the neutral condition in plasma. In such a case, when an antibody that neutralizes the function of a soluble antigen by binding to the antigen is administered to mice in which the concentration of the soluble antigen is maintained constant in plasma, the soluble antigen in plasma forms a complex with the antibody. The soluble antigen incorporated into cells while remaining as the complex is thought to be recycled, in a state bound to the antibody, to the plasma together with the antibody, because the Fc region of the antibody binds to FcRn under the acidic condition in the endosome.

Meanwhile, when the antibody against the soluble antigen is an antibody that binds to the antigen in a pH-dependent manner (i.e., an antibody that dissociates the soluble antigen under the acidic condition in the endosome), the soluble antigen that is non-specifically incorporated into cells while remaining as a complex with the antibody, is dissociated from the antibody in the endosome and degraded in the lysosome; thus, the soluble antigen is not recycled to the plasma. That is, it is thought that Fv4-IgG1 incorporated as a complex with the soluble antigen into cells can dissociate the soluble antigen in the endosome and thus accelerate the elimination of the soluble antigen.

As described above, antigen-binding molecules such as Fv4-IgG1, which contain an antigen-binding domain whose antigen-binding activity is altered depending on the ion concentration, are thought to be capable of binding to antigens repeatedly several times. The effect to accelerate the elimination of soluble antigens from the plasma by dissociating them in the endosome is thought to depend on the rate of incorporation of the antigen/antigen-binding molecule complex into the endosome. An antigen-binding molecule whose binding activity to various FcγRs has been increased and that contains an antigen-binding domain whose antigen-binding activity is altered depending on the condition of ion concentration, is actively incorporated into cells by binding to various FcγRs expressed on the cell membrane, and can be shuttled back to plasma by recycling via the binding between FcRn and the FcRn-binding domain comprised in the molecule, which has FcRn-binding activity under an acidic pH range condition. That is, it is thought that, since the above antigen-binding molecule which forms a complex with a soluble antigen in plasma is actively incorporated into cells via FcγR expressed on the cell membrane, its effect to accelerate the elimination of the soluble antigen from plasma is more markedly shown than antigen-binding molecules whose binding activity to various FcγRs has not been increased.

The FcγR-binding activity of an antibody that binds to a membrane antigen plays an important role in the cytotoxic activity of the antibody. Thus, when it is necessary for an antibody used as a pharmaceutical agent to have cytotoxic activity, a human IgG1 isotype with strong FcγR-binding activity is used. In addition, techniques to enhance the cytotoxic activity of such antibodies by increasing the FcγR-binding activity of the antibodies are used commonly in the art.

Meanwhile, the role of the FcγR-binding activity of antibodies that bind to soluble antigens and which are used as pharmaceutical agents has not been known in the art. There has been no sufficient assessment on what difference in the effect on the living organism administered with the antibodies is caused by the difference in the FcγR-binding activity between human IgG1 with high FcγR-binding activity and human IgG2 and human IgG4 with low FcγR-binding activity. Actually, it was demonstrated in the present Example that there was no influence on the time course of soluble antigen concentration in the plasma of the individuals administered with an antibody that lacks FcγR-binding activity. Meanwhile, in the present invention, it was revealed that the soluble antigen concentration was significantly reduced in the plasma of the individuals administered with an antigen-binding molecule whose FcγR-binding activity has been increased and which contains an antigen-binding domain whose soluble antigen-binding activity is altered depending on the ion concentration condition. Specifically, it can be said that the present inventors revealed for the first time the benefit of the enhancement of FcγR binding by combining an FcRn-binding domain that has FcRn-binding activity under an acidic pH range condition with an antigen-binding domain whose soluble antigen binding is altered depending on the ion concentration condition, comprised in an antigen-binding molecule targeted to a soluble antigen.

Reference Example 8 Effect of Eliminating Antigens from Plasma by Antigen-Binding Molecules Whose FcγR-Binding Activity is Greater than that of Native Human IgG Fc Region and Whose Human FcRn-Binding Activity has been Increased Under an Acidic pH Range Condition

(8-1) Preparation of Antigen-Binding Molecules Whose FcγR-Binding Activity is Greater than the Binding Activity of Native Human IgG Fc Region and Whose Human FcRn-Binding Activity has been Increased Under an Acidic pH Range Condition

A reported method for improving the retention of IgG antibody in plasma is to improve the FcRn binding under an acidic pH range condition. It is thought that, when the FcRn binding under an acidic pH range condition is improved by introducing an amino acid substitution into the Fc region of an IgG antibody, this increases the recycling efficiency from the endosome to plasma, resulting in an improvement of the plasma retention of the IgG antibody.

There are many reports on amino acid alterations to improve the plasma retention by improving the human FcRn-binding activity under an acidic pH range condition. Such alterations include, for example:

the method for substituting Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in an IgG antibody (Nat. Biotechnol, (2010) 28, 157-159); the method for substituting Ala for Asn at position 434 (Drug. Metab. Dispos. (2010) 38 (4), 600-605); the method for substituting Tyr for Met at position 252, Thr for Ser at position 254, and Glu for Thr at position 256 (J. Biol. Chem. (2006) 281, 23514-23524); the method for substituting Gln for Thr at position 250 and Leu for Met at position 428 (J. Immunol. (2006) 176 (1) 346-356); the method for substituting His for Asn at position 434 (Clin. Pharm. & Ther. (2011) 89 (2) 283-290.); and WO2010/106180; WO2010/045193; WO2009/058492; WO2008/022152; WO2006/050166, WO2006/053301, WO2006/031370; WO2005/123780; WO2005/047327; WO2005/037867; WO2004/035752; and WO2002/060919.

VH3-IgG1-F1093 (SEQ ID NO: 125) with a substitution of Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in VH3-IgG1-F1022 was prepared to improve the pharmacokinetics of Fv4-IgG1-F1022 that was demonstrated to produce, when administered, the effect of significantly reducing the soluble antigen concentration in plasma, as described in Reference Example 7. Fv4-IgG-F1093 comprising VH3-IgG1-F1093 as the heavy chain and VL3-CK as the light chain was constructed using the method described in Reference Example 1.

(8-2) Effect of Eliminating Antigens from Plasma by Antigen-Binding Molecules Whose FcγR-Binding Activity is Greater than that of Native Human IgG Fc Region and Whose Human FcRn-Binding Activity has been Increased Under an Acidic pH Range Condition

An in vivo infusion test was carried out for Fv4-IgG1-F1093 by the same method as described in (7-1-1) using human FcRn transgenic mice in which the soluble human IL-6 receptor concentration is maintained constant in plasma Soluble human IL-6 receptor concentrations in the plasma of the mice were determined by the method described in (7-1-2). The result is shown in FIG. 18.

(8-2-1) Determination of the Anti-Human IL-6 Receptor Antibody Concentration in Plasma by ELISA

Anti-human IL-6 receptor antibody concentrations in the plasma of the mice were determined by ELISA. First, an anti-Fv4 ideotype antibody (in-house preparation) was aliquoted in a Nunc-Immuno Plate, MaxiSorp (Nalge nunc International). The plate was allowed to stand at 4° C. overnight to prepare a plate immobilized with the anti-Fv4 ideotype antibody. Standard curve samples with a concentration of 6.4, 3.2, 1.6, 0.8, 0.4, 0.2, or 0.1 μg/ml plasma, and assay samples of mouse plasma diluted 100 times or more were prepared. 100 μl of the standard curve and plasma assay samples were mixed with 200 μl of 20 ng/ml hsIL-6R and 2 mg/ml Sanglopor. This was allowed to stand at one hour at room temperature, and then aliquoted into a plate immobilized with an anti-Fv4 ideotype antibody. The plate was allowed to stand at room temperature for one hour. Then, Biotinylated Anti-human IL-6 R Antibody (R&D) was reacted at room temperature for one hour. Next, Streptavidin-PolyHRP80 (Stereospecific Detection Technologies) was reacted at room temperature for one hour. Chromogenic reaction was performed using TMB One Component HRP Microwell Substrate (BioFX Laboratories) as a substrate. After terminating the reaction with 1N sulfuric acid (Showa Chemical), the absorbance at 450 nm was measured with a microplate reader. The concentrations in mouse plasma were determined based on the absorbance of the standard curve using the analysis software SOFTmax PRO (Molecular Devices). The result is shown in FIG. 19.

(8-3) Improvement of Pharmacokinetics by Increasing the Human FcRn-Binding Activity Under an Acidic pH Range Condition

As shown in FIG. 19, in the group administered with Fv4-IgG1-F1022 resulting from the enhancement of the FcγR-binding activity of Fv4-IgG1 under a neutral pH range condition, the plasma retention of the administered antibody was demonstrated to be reduced as compared to the group administered with Fv4-IgG1. Meanwhile, in the group administered with Fv4-IgG1-F1093 resulting from the enhancement of the human FcRn-binding activity of Fv4-IgG1-F1022 under an acidic pH range condition, the plasma retention of the administered antibody was demonstrated to be significantly improved as compared to the group administered with Fv4-IgG1-F1022.

Furthermore, as shown in FIG. 18, the time course of the soluble human IL-6 receptor concentration in the plasma of the Fv4-IgG1-F1022-administered group was equivalent to that of the Fv4-IgG1-F1093-administered group, up to three days after antibody administration. On day three after administration, as compared to the Fv4-IgG1-administered group, the soluble human IL-6 receptor concentration in plasma was reduced as much as 100 times in both of the Fv4-IgG1-F1022 and Fv4-IgG1-F1093-administered groups. However, on day seven after antibody administration, the soluble human IL-6 receptor concentration in plasma was observed to be elevated in the Fv4-IgG1-F1022-administered group as compared to on day three after administration. On the other hand, in the Fv4-IgG1-F1093-administered group, an increase in the plasma concentration of soluble human IL-6 receptor was not observed, showing that the effect to reduce the soluble human IL-6 receptor concentration was sustained in this administration group.

Specifically, Fv4-IgG1-F1093, when administered, reduced the soluble human IL-6 receptor concentration in the plasma of the administered individual down to about 1/100 as compared to Fv4-IgG1, and in addition, it sustained this condition for a long period. Thus, Fv4-IgG1-F1093 was demonstrated to be a highly excellent antigen-binding molecule. Without being bound by a particular theory, the phenomenon observed herein can be explained as follows. Fv4-IgG1-F1022 in which the FcγR-binding activity of Fv4-IgG1 has been increased under a neutral pH range condition is thought to be incorporated in a large amount mainly into cells expressing FcγR on the cell membrane. The incorporated antibody is transferred into the endosome, and by binding to FcRn in the endosome, the antibody is recycled to the plasma. When the FcRn-binding activity of the antibody is not high enough under the condition at acidic pH in the endosome, the antibody incorporated into the endosome is thought to be incapable of sufficient recycling. Specifically, a possible reason for the reduced plasma retention of Fv4-IgG1-F1022 relative to Fv4-IgG1 would be that the FcRn-binding activity under an acidic pH range condition is insufficient for sufficient recycling of the endosome-incorporated antibody to the plasma by FcRn binding, and the antibody that was not recycled was degraded in the lysosome.

On the other hand, as with Fv4-IgG1-F1022, Fv4-IgG1-F1093 resulting from the enhancement of the human FcRn-binding activity of Fv4-IgG1-F1022 under an acidic pH range condition is thought to be incorporated in a large amount mainly into cells expressing FcγR on the cell membrane. An antibody incorporated and transferred into the endosome is recycled to the plasma by binding to FcRn in the endosome. Since its human FcRn-binding activity under an acidic pH range condition is enhanced, Fv4-IgG1-F1093 is thought to have sufficient FcRn-binding activity in the endosome. Thus, after incorporation into cells, most of Fv4-IgG1-F1093 is recycled to the plasma. Thus, it would be thought that the plasma retention of Fv4-IgG1-F1093 was improved in administered individuals as compared to Fv4-IgG1-F1022.

On the other hand, it has been known that the plasma retention of ordinary antibodies is improved when their FcRn-binding activity is improved under an acidic pH range condition. However, it is thought that, when the antibody retention in plasma is improved, the plasma retention of antibody-bound antigens is also improved, and this results in an increase of the antigen concentration in plasma. In actual, as described in WO2010/088444, Antibody 18E introduced with the alteration YTE into Antibody 18, which is a human IgG1 antibody against IL-6, to increase the FcRn-binding activity under an acidic pH range condition, showed improved antibody retention in the plasma of cynomolgus monkeys, and at the same time, the concentration of the IL-6 antigen was also elevated in the plasma.

Surprisingly, however, when administering Fv4-IgG1-F1093 introduced with an alteration similar to YTE for increasing the FcRn-binding activity under an acidic pH range condition into Fv4-IgG1-F1022 that binds to the antigen in a pH-dependent manner and has increased FcγR-binding activity, the plasma retention of the antibody was significantly improved in the administered individuals without increasing the concentration of soluble human IL-6 receptor which is the antigen. Rather, on day seven after antibody administration, the soluble human IL-6 receptor concentration remained low in the individuals administered with Fv4-IgG1-F1093 as compared to those administered with Fv4-IgG1-F1022.

Without being bound by a particular theory, the phenomenon observed herein can be explained as follows. When administered to a living organism, an antibody without pH-dependent antigen binding is non-specifically incorporated into cells. Antigens that remain to be bound to the antibody are recycled to the plasma in the same extent as the antibody. Meanwhile, for an antibody with increased FcRn-binding activity under an acidic pH range condition, the extent of recycling to the plasma in a living organism administered with the antibody is higher than that of an antibody without increased FcRn-binding activity, and this results in an increased extent of recycling of antigens bound to the antigen to the plasma in the living organism. Thus, due to the improved plasma retention of the antibody administered in the living organism, the plasma concentration of the antigen to which the antibody binds is thought to be also increased in the living organism.

Meanwhile, when administered to a living organism, an antibody that binds to an antigen in a pH-dependent manner and which has increased FcγR-binding activity is mainly incorporated into cells expressing FcγR on the cell membrane, and this worsens the plasma retention. Furthermore, after being incorporated into the cells while bound to the antibody, the antigen is dissociated from the antibody in the endosome and then degraded in the lysosome, resulting in a decrease of the antigen concentration in plasma in the living organism. When the FcRn-binding activity is increased under an acidic pH range condition, the antibody retention in plasma, even if worsened due to increased FcγR-binding activity, is improved by an increase in the rate of recycling by FcRn. In this case, since the antigen bound to the antibody that binds to the antigen in a pH-dependent manner is dissociated from the antibody in the endosome and directly degraded in the lysosome, it is not thought that the antigen concentration is increased in the plasma. Furthermore, the improved plasma retention of the antibody administered to the living organism is thought to allow the antigen elimination effect of the antibody to be sustained, and the antigen concentration to be maintained low for a longer period.

The above findings demonstrate that the plasma retention of an administered antibody is improved in a living organism administered with the antibody in which the human FcRn-binding activity under an acidic pH range condition is enhanced in an antigen-binding molecule whose FcγR-binding activity is higher than that of native human IgG Fc region. Furthermore, it was revealed that, in this case, the antibody retention in plasma is improved without deteriorating the antigen-elimination effect.

Reference Example 9 Further Assessment of the Effect of Eliminating Antigens from Plasma by Antigen-Binding Molecules Whose FcγR-Binding Activity is Greater than that of Native Human IgG Fc Region and Whose Human FcRn-Binding Activity has been Increased Under an Acidic pH Range Condition

(9-1) The Antigen Elimination Effect of an Antibody with Increased FcγR-Binding Activity

As described in Reference Example 7, the antigen concentration in plasma was significantly reduced in the group administered with Fv4-IgG1-F1022 with enhanced mouse FcγR binding. Meanwhile, as shown in Reference Example 8, the reduced plasma retention observed in the Fv4-IgG1-F1022-administered group was markedly improved by increasing the human FcRn-binding activity of Fv4-IgG1-F1022 under an acidic pH range condition. Next, the effect of eliminating soluble antigens from plasma by enhancing mouse FcγR binding and the effect of improving the plasma antibody retention by enhancing the human FcRn binding activity under an acidic pH range condition were further assessed as described below.

(9-2) Preparation of an Anti-Human IL-6 Receptor Antibody with Enhanced Mouse FcγR Binding

VH3-IgG1-F1087 (SEQ ID NO: 145) resulting from substituting Asp for Lys at position 326 (EU numbering) in VH3-IgG1, and VH3-IgG1-F1182 (SEQ ID NO: 148) resulting from substituting Asp for Ser at position 239 and Glu for Ile at position 332 (EU numbering) in VH3-IgG1, were prepared as antigen-binding molecules with enhanced mouse FcγR binding. Fv4-IgG1-F1087 that contains VH3-IgG1-F1087 as the heavy chain and VL3-CK as the light chain, and Fv4-IgG1-F1182 that contains VH3-IgG1-F1182 as the heavy chain and VL3-CK as the light chain, were produced using the method described in Reference Example 1.

(9-3) Assessment of Mouse FcγR-Binding Activity

VH3/L (WT)-IgG1-F1087 and VH3/L (WT)-IgG1-F1182 which contain VH3-IgG1-F1087 and VH3-IgG1-F1182 as the heavy chain, respectively, and L (WT)-CK (SEQ ID NO: 5) as the light chain, were prepared by the method described in Reference Example 1. These antibodies, VH3/L (WT)-IgG1-F1022, and VH3/L (WT)-IgG1 were assessed for their mouse FcγR-binding activity by the method described in Reference Example 2. The result is shown in Table 18. In addition, the ratio of the increase in the mouse FcγR-binding activity of each variant relative to the IgG1 before alteration is shown in Table 19. In the table, VH3/L (WT)-IgG1 is abbreviated as IgG1; VH3/L (WT)-IgG1-F1022 is abbreviated as F1022; VH3/L (WT)-IgG1-F1087 is abbreviated as F1087; and VH3/L (WT)-IgG1-F1182 is abbreviated as F1182.

TABLE 18 KD (M) VARIANT NAME mFcγRI mFcγRIIb mFcγRIII mFcγRIV IgG1 5.3E−08 9.8E−07 2.4E−06 8.6E−08 F1022 7.6E−09 1.0E−08 5.5E−09 1.4E−07 F1087 2.9E−08 5.6E−08 5.2E−08 3.3E−07 F1182 2.4E−09 1.1E−07 4.8E−07 5.3E−10

TABLE 19 RATIO OF BINDING TO IgG1 VARIANT NAME mFcγRI mFcγRIIb mFcγRIII mFcγRIV IgG1 1.0 1.0 1.0 1.0 F1022 7.0 93.6 440.5 0.6 F1087 1.8 17.5 46.2 0.3 F1182 22.1 9.1 5.0 162.3

As shown in Table 19, it was demonstrated that F1087 and F1022 had increased binding activity to mouse FcγRI, mouse FcγRIIb, and mouse FcγRIII as compared to IgG1, whereas their mouse FcγRIV-binding activity was not increased. Regarding the binding activity of F1087 to mouse FcγRI, mouse FcγRIIIb, mouse FcγRIII, and mouse FcγRIV, the extent of its increase was revealed to be smaller than that of F1022. Meanwhile, it was shown that the binding activity of F1182 to mouse FcγRI and mouse FcγRIV was considerably increased, whereas the extent of increase in its binding activity to FcγRIIb and FcγRIII was smaller than those of F1022 and F1087. As mentioned above, these three types of variants showed enhanced binding to some mouse FcγRs; however, it was shown that the FcγR to which the binding activity is selectively increased and the extent of the increase vary depending on the variant.

(9-4) The Effect of Eliminating Antigens from Plasma by Fv4-IgG1-F1087 and Fv4-IgG1-F1182

By the same method as described in Reference Example 7, in vivo infusion tests using human FcRn transgenic mice were carried out to determine the soluble human IL-6 receptor concentrations in the plasma of the mice. The result is shown in FIG. 20.

In both of the groups administered with Fv4-IgG1-F1087 and Fv4-IgG1-F1182 in vivo, which have increased mouse FcγR-binding activity as compared to Fv4-IgG1, the in vivo plasma concentration of soluble human IL-6 receptor was able to be reduced as compared to the group administered with Fv4-IgG1. The effect to reduce the plasma concentration of soluble human IL-6 receptor was high especially in the group administered with Fv4-IgG1-F1087 which has enhanced binding to mouse FcγRII and mouse FcγRIII. Meanwhile, the effect of F1182 administration to reduce the plasma concentration of soluble human IL-6 receptor was small in the group administered with F1182 in vivo which has considerably increased binding activity to mouse FcγRI and mouse FcγRIV (as well as several-fold enhanced binding to mouse FcγRII and mouse FcγRIII). It was thought from these results that the mouse FcγRs that more significantly contribute to the efficient decrease of the antigen concentration in mouse plasma by administration of a pH-dependent antigen-binding antibody, are mouse FcγRII and/or mouse FcγRIII. Specifically, it is thought that the plasma antigen concentration can be more efficiently reduced in vivo by administering into a living organism a pH-dependent antigen-binding antibody with enhanced binding to mouse FcγRII and/or mouse FcγRIII.

(9-5) Preparation of Antigen-Binding Molecules Whose FcγR-Binding Activity is Greater than the Binding Activity of Native Human IgG Fc Region and which have Increased Human FcRn-Binding Activity Under an Acidic pH Range Condition

As described in Reference Example 8, when compared to human FcRn transgenic mice administered with Fv4-IgG1-F1022, the plasma antibody retention is markedly improved in human FcRn transgenic mice administered with Fv4-IgG-F1093 resulting from increasing the human FcRn-binding activity under an acidic pH range condition of Fv4-IgG1-F1022 in which the mouse FcγR-binding activity has been increased. Whether this effect is also observed in human FcRn transgenic mice administered with Fv4-IgG1-F1087 and Fv4-IgG1-F1182, and whether the same effect is observed in mice administered with variants which have increased human FcRn-binding activity under an acidic pH range condition by addition of an alteration distinct from the alteration assessed in Reference Example 8 were assessed as follows.

VH3-IgG1-F1180 (SEQ ID NO: 146) and VH3-IgG1-F1181 (SEQ ID NO: 147) were prepared by substituting Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in the heavy chains VH3-IgG1-F1087 and VH3-IgG1-F1182, respectively, in order to increase their human FcRn-binding activity of Fv4-IgG1-F1087 and Fv4-IgG1-F1182 under an acidic pH range condition. Furthermore, VH3-IgG1-F1412 (SEQ ID NO: 149) was prepared by substituting Ala for Asn at position 434 (EU numbering) in the heavy chain VH3-IgG1-F1087, in order to increase the human FcRn-binding activity of Fv4-IgG1-F1087 under an acidic pH range condition. Fv4-IgG1-F180, Fv4-IgG1-F1181, and Fv4-IgG1-F1412, which contain the above heavy chains and VL3-CK as the light chain, were prepared using the method described in Reference Example 1.

(9-6) Improvement of Pharmacokinetics by Increasing the Human FcRn-Binding Activity Under an Acidic pH Range Condition

In vivo infusion tests were carried out by administering Fv4-IgG1-F1180, Fv4-IgG1-F1181, and Fv4-IgG1-F1412 to human FcRn transgenic mice according to the same method as described in Reference Example 7 to determine the soluble human IL-6 receptor concentrations in the plasma of the mice. The results on the soluble human IL-6 receptor concentrations in the plasma of the mouse groups administered with Fv4-IgG1-F1087, Fv4-IgG1-F1180, Fv4-IgG1-F1412, and Fv4-IgG1 are shown in FIG. 23. The results on the soluble human IL-6 receptor concentrations in the plasma of the mouse groups administered with Fv4-IgG-F1182, Fv4-IgG1-F1181, and Fv4-IgG1 are shown in FIG. 24. Meanwhile, the plasma antibody concentrations in the mouse groups were measured by the method described in Reference Example 8. The results on the plasma antibody concentrations of Fv4-IgG1-F1087, Fv4-IgG1-F1180, Fv4-IgG1-F1412, and Fv4-IgG1 in the mouse groups are shown in FIG. 21, and the results on the plasma antibody concentrations of Fv4-IgG1-F1182, Fv4-IgG1-F1181, and Fv4-IgG1 are shown in FIG. 22.

It was confirmed that, as compared to the group of mice administered with Fv4-IgG1-F1182, the plasma antibody retention was improved in the group of mice administered with Fv4-IgG1-F1181 resulting from increasing the human FcRn-binding activity of Fv4-IgG1-F1182 in an acidic pH range. Meanwhile, the soluble human IL-6 receptor concentration in the plasma of the mouse groups administered with Fv4-IgG1-F1181 was comparable to that in the group of mice administered with Fv4-IgG1-F1182. When compared to the mouse groups administered with Fv4-IgG1, the soluble human IL-6 receptor concentration in the plasma was decreased in both groups.

On the other hand, as compared to the group of mice administered with Fv4-IgG1-F1087, the plasma antibody retention was improved in both groups of mice administered with Fv4-IgG1-F1180 and Fv4-IgG1-F1412 resulting from increasing the human FcRn-binding activity of Fv4-IgG1-F1087 in an acidic pH range, and surprisingly, the plasma retention was improved up to a level comparable to that of the mouse groups administered with Fv4-IgG1. Furthermore, the sustainability of the effect of reducing the soluble human IL-6 receptor concentration in plasma was improved by the improvement of the plasma antibody retention in the groups of administered mice. Specifically, in the groups of administered mice, the soluble human IL-6 receptor concentrations in plasma 14 days and 21 days after administration of Fv4-IgG1-F1180 and Fv4-IgG1-F1412 were significantly reduced as compared to the concentrations 14 days and 21 days after administration of Fv4-IgG1-F1087.

In view of the above, as for the groups of mice administered with the four examples of antibodies, Fv4-IgG1-F093, Fv4-IgG1-F1181, Fv4-IgG1-F1180, and Fv4-IgG1-F1412, it was demonstrated that the plasma retention can be improved in a living organism administered with an antibody in which the human FcRn-binding activity under an acidic pH range condition is enhanced in an antigen-binding molecule whose FcγR-binding activity is higher than the binding activity of native human IgG Fc region. It was also demonstrated that, in the living organism administered with the antigen-binding molecule, the plasma retention is improved without deteriorating the effect of eliminating antigens from the living organism, and rather, the antigen elimination effect can be sustained.

It was shown that the alteration that increases the human FcRn-binding activity under an acidic pH range condition can be achievable by not only a method for substituting Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering), but also a method for substituting Ala for Asn at position 434 (EU numbering). Thus, alterations used for increasing the human FcRn-binding activity under an acidic pH range condition are not particularly limited, and include:

the method for substituting Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in an IgG antibody (Nat. Biotechnol. (2010) 28, 157-159); the method for substituting Ala for Asn at position 434 (Drug Metab. Dispos. (2010) 38 (4) 600-605); the method for substituting Tyr for Met at position 252, Thr for Ser at position 254, and Glu for Thr at position 256 (J. Biol. Chem. (2006) 281, 23514-23524); the method for substituting Gln for Thr at position 250 and Leu for Met at position 428 (J. Immunol. (2006) 176 (1), 346-356); and the method for substituting His for Asn at position 434 (Clin. Pharmcol. Ther. (2011) 89 (2) 283-290), and the alterations described in WO2010/106180, WO2010/045193, WO2009/058492, WO2008/022152, WO2006/050166; WO2006/053301, WO2006/031370, WO2005/123780, WO2005/047327, WO2005/037867, WO2004/035752, and WO2002/060919, etc. (9-7) Preparation of Antigen-Binding Molecules with Increased Human FcRn-Binding Activity Under an Acidic pH Range Condition and Suppressed Binding to a Rheumatoid Factor

In recent years, an antibody molecule resulting from substituting His for Asn at position 434 (EU numbering) in a humanized anti-CD4 antibody to improve the plasma retention by increasing its human FcRn-binding activity under an acidic pH range condition, has been reported to bind to the rheumatoid factor (RF) (Clin. Pharmacol. Ther. (2011) 89 (2), 283-290). This antibody has a human IgG1 Fc region and a substitution of His for Asn at position 434 (EU numbering) in the FcRn-binding site. The rheumatoid factor has been demonstrated to recognize and bind to the substituted portion.

As shown in (9-6), various alterations have been reported to increase the human FcRn-binding activity under an acidic pH range condition. There is the possibility that the binding activity to the rheumatoid factor that recognizes the site is increased by introducing such alterations into the FcRn-binding site of the Fc region.

However, antigen-binding molecules that have increased human FcRn-binding activity under an acidic pH range condition but do not have the binding to the rheumatoid factor can be produced by introducing into the site of the Fc region an alteration that reduces the rheumatoid factor-binding activity alone without reducing the FcRn-binding activity under an acidic pH range condition.

Such alterations used for reducing the rheumatoid factor-binding activity include alterations at positions 248-257, 305-314, 342-352, 380-386, 388, 414-421, 423, 425-437, 439, and 441-444 (EU numbering), preferably those at positions 387, 422, 424, 426, 433, 436, 438, and 440 (EU numbering), and particularly preferably, an alteration that substitutes Glu or Ser for Val at position 422, an alteration that substitutes Arg for Ser at position 424, an alteration that substitutes Asp for His at position 433, an alteration that substitutes Thr for Tyr at position 436, an alteration that substitutes Arg or Lys for Gln at position 438, and an alteration that substitutes Glu or Asp for Ser at position 440 (EU numbering). These alterations may be used alone or in combination.

Alternatively, it is possible to introduce N-type glycosylation sequences to reduce the rheumatoid factor-binding activity. Specifically, known N-type glycosylation sequences include Asn-Xxx-Ser/Thr (Xxx represents an arbitrary amino acid other than Pro). This sequence can be introduced into the Fc region to add an N-type sugar chain, and the binding to RF can be inhibited by the steric hindrance of the N-type sugar chain. Alterations used for adding an N-type sugar chain preferably include an alteration that substitutes Asn for Lys at position 248, an alteration that substitutes Asn for Ser at position 424, an alteration that substitutes Asn for Tyr at position 436 and Thr for Gln at position 438, and an alteration that substitutes of Asn for Qln at position 438, according to EU numbering, particularly preferably an alteration that substitutes Asn for Ser at position 424 (EU numbering).

Reference Example 10 Effect of Eliminating Antigens from Plasma by Antigen-Binding Molecules Whose FcγR-Binding Activity is Higher than the Binding Activity of Native Mouse IgG Fc Region

(10-1) The Antigen Elimination Effect of Mouse Antibodies with Increased FcγR-Binding Activity

As described in Reference Examples 6 to 9, it was demonstrated that the elimination of soluble human IL-6 receptor from mouse plasma is accelerated in the groups of human FcRn transgenic mice administered with antigen-binding molecules resulting from increasing the mouse FcγR-binding activity of antigen-binding molecules that have a human antibody Fc region and the property of binding to human IL-6 receptor in a pH-dependent manner. Whether this effect is also achieved in normal mice having mouse FcRn that was administered with antigen-binding molecules that have a mouse antibody Fc region and the property of binding to human IL-6 receptor in a pH-dependent manner, was assessed as follows.

(10-2) Preparation of Mouse Antibodies with Increased FcγR-Binding Activity

For a mouse IgG1 antibody having the property of binding to human IL-6 receptor in a pH-dependent manner, the heavy chain VH3-mIgG1 (SEQ ID NO: 150) and the light chain VL3-mk1 (SEQ ID NO: 151) were constructed using the method described in Reference Example 1. Meanwhile, to increase the mouse FcγR-binding activity of VH3-mIgG1, VH3-mIgG1-mF44 (SEQ ID NO: 152) was produced by substituting Asp for Ala at position 327 (EU numbering). Likewise, VH3-mIgG1-mF46 (SEQ ID NO: 153) was produced by substituting Asp for Ser at position 239 and Asp for Ala at position 327, according to EU numbering, in VH3-mIgG1. Fv4-mIgG1, Fv4-mIgG1-mF44, and Fv4-mIgG1-mF46, which contain VH3-mIgG1. VH3-mIgG1-mF44, and VH3-mIgG1-mF46, respectively, as the heavy chain, and VL3-mk1 as the light chain, were prepared using the method described in Reference Example 1.

(10-3) Assessment of Mouse FcγR-Binding Activity

VH3/L (WT)-mIgG1, VH3/L (WT)-mIgG1-mF44, and VH3/L (WT)-mIgG1-mF46, which contain VH3-mIgG1, VH3-mIgG1-mF44, and VH3-mIgG1-mF46, respectively, as the heavy chain, and L (WT)-CK (SEQ ID NO: 5) as the light chain, were prepared by the method described in Reference Example 1. These antibodies were assessed for their mouse FcγR-binding activity by the method described in Reference Example 2. The result is shown in Table 20. In addition, the ratio of the increase in the mouse FcγR-binding activity of each variant relative to the mIgG1 before alteration is shown in Table 21. In the table, VH3/L (WT)-mIgG1 is abbreviated as mIgG1; VH3/L (WT)-mIgG1-mF44 is abbreviated as mF44; and VH3/L (WT)-mIgG1-mF46 is abbreviated as mF46.

TABLE 20 KD (M) VARIANT NAME mFcγRI mFcγRIIb mFcγRIII mFcγRIV mIgG1 NOT 1.1E−07 2.1E−07 NOT DETECTED DETECTED mF44 NOT 8.9E−09 6.7E−09 NOT DETECTED DETECTED mF46 NOT 1.2E−09 3.6E−09 NOT DETECTED DETECTED

TABLE 21 RATIO OF BINDING TO mIgG1 VARIANT NAME mFcγRI mFcγRIIb mFcγRIII mFcγRIV mIgG1 NOT 1.0 1.0 NOT DETECTED DETECTED mF44 NOT 11.9 31.0 NOT DETECTED DETECTED mF46 NOT 91.4 57.5 NOT DETECTED DETECTED

The assessment result of Reference Example 9 showing that VH3/L (WT)-mIgG1 having the Fc region of native mouse IgG antibody only binds to mouse FcγRIIb and mouse FcγRIII but not to mouse FcγRI and mouse FcγRIV, suggests that mouse FcγRs important for the reduction of antigen concentration are mouse FcγRII and/or mouse FcγRIII. VH3/L (WT)-mIgG-mF44 and VH3/L (WT)-mIgG1-mF46 introduced with an alteration that is thought to increase the FcγR-binding activity of VH3/L (WT)-mIgG1 was demonstrated to have increased binding activity to both of mouse FcγRIIb and mouse FcγRIII.

(10-4) Assessment of the Effect to Reduce the Soluble Human IL-6 Receptor Concentration in the Plasma of Normal Mice

The effect to eliminate soluble human IL-6 receptor from the plasma of normal mice administered with the anti-human IL-6 receptor antibody Fv4-mIgG1, Fv4-mIgG1-mF44, or Fv4-mIgG1mF46 was assessed as follows.

An animal model where the soluble human IL-6 receptor concentration is maintained in a steady state in plasma was created by implanting an infusion pump (MINI-OSMOTIC PUMP MODEL2004, alzet) containing soluble human IL-6 receptor under the skin on the back of normal mice (C57BL/6J mouse, Charles River Japan). The in vivo kinetics of soluble human IL-6 receptor after administration of the anti-human IL-6 receptor antibody was assessed in the animal model. To suppress the production of antibodies against soluble human IL-6 receptor, an anti-mouse CD4 monoclonal antibody was administered once at 20 mg/kg into the tail vein. Then, an infusion pump containing 92.8 μg/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice. Three days after implantation of the infusion pump, the anti-human IL-6 receptor antibody was administered once at 1 mg/kg into the tail vein. The blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, seven days, 14 days (or 15 days), and 21 days (or 22 days) after administration of the anti-human IL-6 receptor antibody. Immediately thereafter, the collected blood was centrifuged at 15,000 rpm and 4° C. for 15 minutes to prepare the plasma. The isolated plasma was stored in a freezer set at −20° C. or below until use.

The soluble human IL-6 receptor concentrations in plasma were determined by the method described in (7-1-2). The result is shown in FIG. 25.

Surprisingly, it was demonstrated that, in mice administered with mF44 and mF46 introduced with an alteration to increase the binding activity of mIgG1 (native mouse IgG1) to mouse FcγRIIb and mouse FcγRIII, the plasma IL-6 receptor concentration was markedly reduced as compared to mice administered with mIgG1. In particular, even on day 21 after administration of mF44, the plasma IL-6 receptor concentration in the mF44-administered group was reduced by about 6 times as compared to the plasma IL-6 receptor concentration in the group without antibody administration, and about 10 times as compared to the mIgG1-administered group. On the other hand, on day seven after administration of mF46, the plasma IL-6 receptor concentration in the mF46-administered group was markedly reduced by about 30 times as compared to the plasma IL-6 receptor concentration in the group without antibody administration, and about 50 times as compared to the mIgG1-administered group.

The above findings demonstrate that the elimination of soluble human IL-6 receptor from plasma was also accelerated in mice administered with antibodies in which the mouse FcγR-binding activity of an antigen-binding molecule having the Fc regions of mouse IgG1 antibody is increased, as with antibodies in which the mouse FcγR-binding activity of an antigen-binding molecule having the Fc region of human IgG1 antibody is increased. Without being bound by a particular theory, the phenomenon observed as described above can be explained as follows.

When administered to mice, antibodies that bind to a soluble antigen in a pH-dependent manner and have increased Fcγ-R-binding activity are actively incorporated mainly into cells expressing FcγR on the cell membrane. The incorporated antibodies dissociate the soluble antigen under an acidic pH condition in the endosome, and then recycled to plasma via FcRn. Thus, a factor that achieves the effect of eliminating the plasma soluble antigen of such an antibody is the FcγR-binding activity level of the antibody. Specifically, as the FcγR-binding activity is greater, the incorporation into FcγR-expressing cells occurs more actively, and this makes the elimination of soluble antigens from plasma more rapid. Furthermore, as long as the FcγR-binding activity has been increased, the effect can be assessed in the same manner regardless of whether the Fc region contained in an antibody originates from human or mouse IgG1. Specifically, the assessment can be achieved for an Fc region of any animal species, such as any of human IgG1, human IgG2, human IgG3, human IgG4, mouse IgG1, mouse IgG2a, mouse IgG2b, mouse IgG3, rat IgG, monkey IgG, and rabbit IgG, as long as the binding activity to the FcγR of the animal species to be administered has been increased.

Reference Example 11 The Antigen Elimination Effect by Antibodies with the Binding Activity Increased in a FcγRIIb-Selective Manner

(11-1) The Antigen Elimination Effect of Antibodies in which the FcγRIIb-Binding Activity has been Selectively Increased

FcγRIII-deficient mice (B6.129P2-FcgrR3tm1Sjv/J mouse, Jackson Laboratories) express mouse FcγRI, mouse FcγRIIb, and mouse FcγRIV, but not mouse FcγRIII. Meanwhile, Fc receptor γ chain-deficient mice (FcerIg mouse, Taconic, Cell (1994) 76, 519-529) express mouse FcγRIIb alone, but not mouse FcγRI, mouse FcγRIII, and mouse FcγRIV.

As described in Reference Example 10, it was demonstrated that mF44 and mF46 with increased FcγR-binding activity of native mouse IgG1 show selectively enhanced binding to mouse FcγRIIb and mouse FcγRIII. It was conceived that, using the selectively increased binding activity of the antibodies, the condition under which an antibody with selectively enhanced mouse FcγRIIb binding is administered can be mimicked by administering mF44 and mF46 to mouse FcγRIII-deficient mice or Fc receptor γ chain-deficient mice which do not express mouse FcγRIII.

(11-2) Assessment of the Antigen Elimination Effect by the Mouse FcγRIIb-Selective Enhancement of Binding Using FcγRIII-Deficient Mice

The effect to eliminate soluble human IL-6 receptor from plasma in FcγRIII-deficient mice administered with the anti-human IL-6 receptor antibody Fv4-mIgG1, Fv4-mIgG1-mF44, or Fv4-mIgG1-mF46 was assessed by the same method described in Reference Example 10. The soluble human IL-6 receptor concentrations in the plasma of the mice were determined by the method described in (7-1-2). The result is shown in FIG. 26.

Surprisingly, it was demonstrated that, the plasma IL-6 receptor concentrations in FcγRIII-deficient mice administered with mF44 and mF46, which mimic the condition under which the mouse FcγRIIb-binding activity of mIgG1 (native mouse IgG1) is selectively increased, were markedly reduced as compared to the plasma IL-6 receptor concentration in mice administered with mIgG1. In particular, the plasma IL-6 receptor concentration of the mF44-administered group was reduced by about three times as compared to that of the mIgG1-administered group and the accumulation of antigen concentration due to antibody administration was suppressed. Meanwhile, on day three after administration, the plasma IL-6 receptor concentration of the mF46-administered group was markedly reduced by about six times as compared to the plasma IL-6 receptor concentration of the group without antibody administration, and about 25 times as compared to the plasma IL-6 receptor concentration of the mIgG1-administered group. This result shows that, as the mouse FcγRIIb-binding activity of an anti-human IL-6 receptor antibody that binds to the antigen in a pH-dependent manner is greater, the IL-6 receptor concentration can be reduced more in the plasma of mice administered with the antibody.

(11-3) Assessment of the Antigen Elimination Effect by the Selective Enhancement of Mouse FcγRIIb Binding Using Fc Receptor γ Chain-Deficient Mice

The effect to eliminate soluble human IL-6 receptor from the plasma of Fc receptor γ chain-deficient mice administered with the anti-human IL-6 receptor antibody Fv4-mIgG1, Fv4-mIgG1-mF44, or Fv4-mIgG1mF46, was assessed by the same method as described in Reference Example 10. The soluble human IL-6 receptor concentrations in the plasma of the mice were determined by the method described in (7-1-2). The result is shown in FIG. 27.

As with the case where mF44 and mF46 were administered to FcγRIII-deficient mice, the plasma IL-6 receptor concentration in Fc receptor γ chain-deficient mice administered with mF44 and mF46, which mimic the condition resulting from the selective increase in the mouse FcγRIIb-binding activity of mIgG1 (native mouse IgG1), was demonstrated to be markedly reduced as compared to the plasma IL-6 receptor concentration in Fc receptor γ chain-deficient mice administered with mIgG1. In particular, the plasma IL-6 receptor concentration in the mF44-administered group was reduced to about three times that in the mIgG1-administered group, and the accumulation of antigen concentration due to antibody administration was suppressed. Meanwhile, on day three after administration, the plasma IL-6 receptor concentration in the mF46-administered group was markedly reduced by about five times as compared to that in the group without antibody administration, and about 15 times as compared to that in the mIgG1-administered group.

The results described in (11-2) and (11-3) show that the soluble antigen concentration in the plasma is markedly reduced in the group administered with an antibody that binds to a soluble antigen in a pH-dependent manner and has selectively increased mouse FcγRIIb-binding activity.

Reference Example 12 The Antigen Elimination Effect of Antibodies with FcγRIII-Selective Binding Enhancement

(12-1) The Antigen Elimination Effect of Antibodies with Selectively Enhanced FcγRIII Binding

FcγRIIb-deficient mice (Fcgr2b (FcγRII) mouse, Taconic) (Nature (1996) 379 (6563), 346-349) express mouse FcγRI, mouse FcγRIII, and mouse FcγRIV, but not mouse FcγRIIb. As described in Reference Example 10, it was demonstrated that mF44 and mF46 resulting from increasing the FcγR-binding activity of native mouse IgG1 show selectively enhanced binding to mouse FcγRIIb and mouse FcγRIII. It was conceived that, based on the use of the selectively increased binding activity of the antibodies, the condition of administration of an antibody with selectively enhanced binding to mouse FcγRIII can be mimicked by administering mF44 or mF46 to mouse FcγRIIb-deficient mice which do not express mouse FcγRIIb.

As described in Reference Example 11, the soluble antigen concentration was reduced in the plasma of FcγRIII-deficient mice, which mimic the condition of administration of an antibody with selectively increased mouse FcγRIIb-binding activity. Meanwhile, whether the soluble antigen concentration is reduced in the plasma of FcγRIIb-deficient mice, which mimic the condition of administration of an antibody with selectively increased mouse FcγRIII-binding activity, was assessed by the test described below.

(12-2) Assessment of the Antigen Elimination Effect by Selective Enhancement of Mouse FcγRIII Binding Using FcγRIIb-Deficient Mice

The effect to eliminate soluble human IL-6 receptor from the plasma of FcγRIIb-deficient mice administered with the anti-human IL-6 receptor antibody Fv4-mIgG1, Fv4-mIgG1-mF44, or Fv4-mIgG1mF46, was assessed by the same method as described in Reference Example 10. The soluble human IL-6 receptor concentrations in plasma were determined by the method described in (7-1-2). The result is shown in FIG. 28.

Surprisingly, in the groups administered with mF44 and mF46, which mimic selective increase of the mouse FcγRIII-binding activity of mIgG1 (native mouse IgG1), the plasma IL-6 receptor concentration was reduced, but the reduction was not as significant as that shown in Reference Example 1.

Without being bound by a particular theory, based on the results described in Reference Examples 10, 11, and 12, the following discussion is possible. The elimination of soluble human IL-6 receptor from plasma was found to be markedly accelerated in normal mice expressing both mouse FcγRIIb and mouse FcγRIII that were administered with mF44 and mF46 with selectively increased binding activity of mIgG1 (native mouse IgG1) to mouse FcγRIIb and mouse FcγRIII. Furthermore, it was revealed that, when mF44 and mF46 were administered to mice that express mouse FcγRIIb but not mouse FcγRIII (i.e., FcγRIII-deficient mice and Fc receptor γ chain-deficient mice), the elimination of soluble human IL-6 receptor from plasma was also accelerated markedly in the mice. Meanwhile, when mF44 and mF46 were administered to mice that express mouse FcγRIII but not mouse FcγRIIb (i.e., FcγRII-deficient mice), the elimination of soluble human IL-6 receptor from plasma was not markedly accelerated in the mice.

From the above findings, it is thought that, the antibodies mF44 and mF46 in which the binding activity of mIgG1 (native mouse IgG1) to mouse FcγRIIb and mouse FcγRIII is selectively increased, are incorporated into FcγR-expressing cells mainly by mouse FcγRIIb, and thus the soluble antigen in the plasma that binds to the antibodies is eliminated. Meanwhile, the FcγRIII-mediated incorporation of antibody/antigen complexes into FcγR-expressing cells is thought not to significantly contribute to the elimination of the soluble antigen from plasma.

Furthermore, as shown in Reference Example 9, the plasma concentration of soluble human IL-6 receptor was markedly reduced in mice administered with Fv4-IgG1-F1087 having increased binding activity to mouse FcγRIIb and mouse FcγRIII, in particular. Meanwhile, the effect to eliminate soluble human IL-6 receptor from the plasma of mice administered with Fv4-IgG1-F1182 with increased binding activity to mouse FcγRI and mouse FcγRIV, in particular, was smaller than that of Fv4-IgG1-F1087.

Furthermore, as shown in Reference Example 7, in mice administered with Fv4-IgG1-Fuc whose mouse FcγRIV-binding activity has been considerably increased by having sugar chains with low fucose content (Science (2005) 310 (5753) 1510-1512), the plasma concentration of soluble human IL-6 receptor was reduced as compared to that in mice administered with Fv4-IgG1; however, the reduction effect was as small as about twice. Thus, mouse FcγRIV-mediated incorporation of antibodies into FcγR-expressing cells is thought not to significantly contribute to the elimination of soluble antigens from plasma.

The above demonstrates that, in mice, of multiple mouse FcγRs, mouse FcγRIIb plays a major role in the incorporation of antibodies into FcγR-expressing cells. Thus, mutations to be introduced into the mouse Fcγ receptor-binding domain are particularly preferably, but are not particularly limited to, mutations that enhance the binding to mouse FcγRIIb.

By this assessment using mice, it was demonstrated that, when an antigen-binding molecule that binds to a soluble antigen in a pH-dependent manner and has increased FcγR-binding activity is administered to accelerate the elimination of the soluble antigen from plasma in the administered living organism, it is more preferable to increase the FcγRIIb-binding activity of the antibody to be administered. Specifically, it was revealed that, when administered to the living organism, antigen-binding molecules that bind to a soluble antigen in a pH-dependent manner and have increased FcγRIIb-binding activity can effectively reduce the plasma concentration of the soluble antigen by accelerating the elimination of the soluble antigen from plasma, and thus such antigen-binding molecules exhibit highly effective action.

Reference Example 1 Assessment of the Platelet Aggregatory Ability of Antibodies Containing an Fc Region Introduced with an Existing Alteration that Enhances the FcγRIIb Binding

(13-1) Preparation of Antibodies Containing an Fc Region Introduced with an Existing Alteration that Enhances the FcγRIIb Binding

As described in Reference Example 12, antigens can be efficiently eliminated from the plasma of the living organism by administering antibodies with selectively increased FcγRIIb-binding activity to the living organism. Furthermore, the administration of antibodies containing an Fc region with selectively increased FcγRIIb-binding activity is thought to be preferred from the viewpoint of safety and side effects in the living organism administered with such antibodies.

However, the mouse FcγRIIb binding and mouse FcγRIII binding are both enhanced in mF44 and mF46, and thus the binding enhancement is not selective for mouse FcγRIIb. Since the homology between mouse FcγRIIb and mouse FcγRIII is high, it would be difficult to find an alteration that enhances the mouse FcγRIIb-selective binding while distinguishing the two. Moreover, there is no previous report on Fc regions with selectively enhanced mouse FcγRIIb binding. In addition, the homology between human FcγRIIb and human FcγRIIa (allotypes H131 and R131) is also known to be high. Furthermore, it has been reported that antibodies with enhanced FcγRIIa binding have increased platelet aggregatory activity, and can increase the risk of developing thrombosis in the living organism administered with them (Meyer et al., (J. Thromb. Haemost. (2009), 7 (1), 171-181), Robles-Carrillo et al., (J. Immunol. (2010), 185 (3), 1577-1583)). Thus, whether antibodies with enhanced FcγRIIa binding have increased platelet aggregatory activity was assessed as follows.

(13-2) Assessment of the Human FcγR-Binding Activity of Antibodies Containing an Fc Region Introduced with an Existing Alteration that Enhances the FcγRIIb Binding

Antibodies containing an Fc region introduced with an existing alteration that enhances the human FcγRIIb binding were analyzed for their affinity for human FcγRIa. R-type and H-type FcγRIIa, FcγRIIb, and FcγRIIIa by the following procedure. An H chain was constructed to have, as the antibody H chain variable region, the antibody variable region IL6R-H (SEQ ID NO: 154) against human IL-6 receptor which is disclosed in WO2009/125825, and as the antibody H chain constant region, IL6R-G1d (SEQ ID NO: 156) that has G1d resulting from removing the C-terminal Gly and Lys from human IgG1. Then, IL6R-G1d-v3 (SEQ ID NO: 157) was constructed by altering the Fc region of IL6R-G1d by the substitution of Glu for Ser at position 267 (EU numbering) and Phe for Leu at position 328 (EU numbering), as described in Seung et al., (Mol. Immunol. (2008) 45, 3926-3933). IL6R-L (SEQ ID NO: 155) which is the L chain of anti-human IL-6 receptor antibody was used as a common antibody L chain, and expressed in combination with respective H chains according to the method described in Reference Example 1, and the resulting antibodies were purified. Hereinafter, antibodies containing IL6R-G1d and IL6R-G1d-v3 as the heavy chain are referred to as IgG1 and IgG1-v3, respectively.

Then, the interaction between FcγR and the above antibodies was kinetically analyzed using Biacore T100 (GE Healthcare). The assay for the interaction was carried out at 25° C. using HBS-EP+(GE Healthcare) as a running buffer. The chip used was a Series S Sencor Chip CM5 (GE Healthcare) immobilized with Protein A by an amine coupling method. Each FcγR diluted with the running buffer was allowed to interact with the antibodies of interest captured onto the chip to measure the binding of the antibodies to each FcγR. After measurement, 10 mM glycine-HCl (pH 1.5) was reacted to the chip to wash off the captured antibodies to repeatedly use the regenerated chip. A sensorgram obtained as a result of the measurement was analyzed using 1:1 Langmuir binding model with Biacore Evaluation Software, and binding rate constant ka (L/mol/s) and dissociation rate constant kd (1/s) were calculated, and the dissociation constant KD (mol/1) was calculated from these values. The KD values of IgG and IgG1-v3 to each FcγR are shown in Table 22 (the KD values of each antibody to each FcγR), while the relative KD values of IgG1-v3, which are obtained by dividing KD of IgG1 to each FcγR by KD of IgG1-v3 to each FcγR, are shown in Table 23.

TABLE 22 KD (M) ANTIBODY FcγRIa FcγRIIaR FcγRIIaH FcγRIIb FcγRIIIa IgG1 3.4E−10 1.2E−06 7.7E−07 5.3E−06 3.1E−06 IgG1-v3 1.9E−10 2.3E−09 1.5E−06 1.3E−08 8.8E−06

TABLE 23 FcγRIa FcγRIIaR FcγRIIaH FcγRIIb FcγRIIIa KD VALUE 1.8 522 0.51 408 0.35 RATIO

The above results show that, as compared to the antibody containing the Fc region of IgG1, the antibody containing an altered Fc region (Mol. Immunol. (2008) 45, 3926-3933) with the substitution of Glu for Ser at position 267 and Phe for Leu at position 328 (EU numbering) in the Fc region of IgG1, its affinity for FcγRIIb has been increased by 408 times; its affinity for H-type FcγRIIa has been reduced to 0.51 times; and its affinity for R-type FcγRIIa has been increased by 522 times.

(13-3) Assessment of the Ability to Aggregate Platelets

Next, whether the increased/reduced FcγRIIa affinity of the antibody containing the Fc region with the substitution of Glu for Ser at position 267 and Phe for Leu at position 328 (EU numbering) in the Fc region of IgG1 changes the platelet aggregatory ability, was assessed using platelets derived from donors with H-type or R-type FcγRIIIa. The antibody comprising as the light chain omalizumab_VL-CK (SEQ ID NO: 159) and omalizumab_VH-G1d (SEQ ID NO: 158) that contains the heavy chain variable region of hIgG1 antibody (human IgG1 constant region) that binds to IgE and the G1d heavy chain constant region, was constructed using the method described in Reference Example 1. Furthermore, omalizumab_VH-G1d-v3 (SEQ ID NO: 160) was constructed by substituting Glu for Ser at position 267 and Phe for Leu at position 328 (EU numbering) in omalizumab_VH-G1d. Omalizumab-G1d-v3, which contains omalizumab_VH-G1d-v3 as the heavy chain and omalizumab_VL-CK as the light chain, was prepared using the method described in Reference Example 1. This antibody was assessed for the platelet aggregatory ability.

Platelet aggregation was assayed using the platelet aggregometer HEMA TRACER 712 (LMS Co.). First, about 50 ml of whole blood was collected at a fixed amount into 4.5-ml evacuated blood collection tubes containing 0.5 ml of 3.8% sodium citrate, and this was centrifuged at 200 g for 15 minutes. The resultant supernatant was collected and used as platelet-rich plasma (PRP). After PRP was washed with buffer A (137 mM NaCl, 2.7 mM KCl, 12 mM NaHCO₃, 0.42 mM NaH₂PO₄, 2 mM MgCl₂, 5 mM HEPES, 5.55 mM dextrose, 1.5 U/ml apyrase, 0.35% BSA), the buffer was replaced with buffer B (137 mM NaCl, 2.7 mM KCl, 12 mM NaHCO₃, 0.42 mM NaH₂PO₄, 2 mM MgCl₂, 5 mM HEPES, 5.55 mM dextrose, 2 mM CaCl₂, 0.35% BSA). This yielded washed platelets at a density of about 300,000/μl, 156 μl of the washed platelets was aliquoted into assay cuvettes containing a stir bar in the platelet aggregometer. The platelets were stirred at 1000 rpm with the stir bar in the cuvettes maintained at 37.0° C. in the platelet aggregometer. 44 μl of the immune complex of omalizumab-G1d-v3 and IgE at a molar ratio of 1:1, prepared at final concentrations of 600 μg/ml and 686 μg/ml, respectively, was added to the cuvettes. The platelets were reacted with the immune complex for five minutes. Then, at a concentration that does not allow secondary platelet aggregation, adenosine diphosphate (ADP, SIGMA) was added to the reaction mixture to test whether the aggregation is enhanced.

The result of platelet aggregation for each donor with an FcγRIIa polymorphic form (H/H or R/H) obtained from the above assay is shown in FIGS. 29 and 30. The result in FIG. 29 shows that platelet aggregation is enhanced when the immune complex is added to the platelets of a donor with the FcγRIIa polymorphic form (R/H). Meanwhile, as shown in FIG. 30, platelet aggregation was not enhanced when the immune complex is added to the platelets of a donor with the FcγRIIa polymorphic form (H/H).

Next, platelet activation was assessed using activation markers. Platelet activation can be measured based on the increased expression of an activation marker such as CD62p (p-selectin) or active integrin on the platelet membrane surface. 2.3 μl of the immune complex was added to 7.7 μl of the washed platelets prepared by the method described above. After five minutes of reaction at room temperature, activation was induced by adding ADP at a final concentration of 30 μM, and whether the immune complex enhances the ADP-dependent activation was assessed. A sample added with phosphate buffer (pH 7.4) (Gibco), instead of the immune complex, was used as a negative control. Staining was performed by adding, to each post-reaction sample, PE-labeled anti-CD62 antibody (BECTON DICKINSON), PerCP-labeled anti-CD61 antibody, and FITC-labeled PAC-1 antibody (BD bioscience). Fluorescence intensity for each stain was measured using a flow cytometer (FACS CantoII, BD bioscience).

The result on CD62p expression, obtained by the above assay method, is shown in FIG. 31. The result on the activated integrin expression is shown in FIG. 32. The washed platelets used were obtained from a healthy person with the FcγRIIa polymorphic form R/H. The expression of both CD62p and active integrin on platelet membrane surface, which is induced by ADP stimulation, was enhanced in the presence of the immune complex.

The above results demonstrate that the antibody having the Fc region introduced with an existing alteration that enhances the human FcγRIIb binding, which is the substitution of Glu for Ser at position 267 and Phe for Leu at position 328 (EU numbering) in the Fc region of IgG1, promotes the aggregation of platelets with the FcγRIIa allotype in which the amino acid at position 131 is R, as compared to platelets with the FcγRIIa polymorphic form in which the amino acid at position 131 is H. That is, it was suggested that the risk of developing thrombosis due to platelet aggregation can be increased when an antibody containing an Fc region introduced with an existing alteration that enhances the human FcγRIIb binding is administered to humans having R-type Fcγ-RIIa. It was shown that the antigen-binding molecules containing an Fc region of the present invention that enhances the FcγRIIb binding more selectively not only improves the antigen retention in plasma, but also possibly solves the above problems. Thus, the usefulness of the antigen-binding molecules of the present invention is obvious.

Reference Example 14 Comprehensive Analysis of FcγRIIb Binding of Variants Introduced with an Alteration at the Hinge Portion in Addition to the P238D Alteration

In an Fc produced by substituting Pro at position 238 (EU numbering) with Asp in a naturally-occurring human IgG1, an anticipated combinatorial effect could not be obtained even by combining it with another alteration predicted to further increase FcγRIIb binding from the analysis of naturally-occurring antibodies. Therefore, in order to find variants that further enhance FcγRIIb binding, alterations were comprehensively introduced into the altered Fc produced by substituting Pro at position 238 (EU numbering) with Asp. IL6R-F11 (SEQ ID NO: 161) was produced by introducing an alteration of substituting Met at position 252 (EU numbering) with Tyr and an alteration of substituting Asn at position 434 (EU numbering) with Tyr in IL6R-G1d (SEQ ID NO: 156) which was used as the antibody H chain. Furthermore, IL6R-F652 (SEQ ID NO: 162) was prepared by introducing an alteration of substituting Pro at position 238 (EU numbering) with Asp into IL6R-F11. Expression plasmids containing an antibody H chain sequence were prepared for each of the antibody H chain sequences produced by substituting the region near the residue at position 238 (EU numbering) (positions 234 to 237, and 239 (EU numbering)) in L6R-F652 each with 18 amino acids excluding the original amino acid and Cys. IL6R-L (SEQ ID NO: 155) was utilized as an antibody L chain. These variants were expressed and purified by the method of Reference Example 1. These Fc variants are called PD variants. Interactions of each PD variant with FcγRIIa type R (allotype R131) and FcγRIIb were comprehensively evaluated by the method of Reference Example 2.

A figure that shows the results of analyzing the interaction with the respective FcγRs was produced according to the following method. The value obtained by dividing the value for the amount of binding of each PD variant to each FcγR by the value for the amount of FcγR binding of the pre-altered antibody which is used as the control (IL6R-F652/IL6R-L, which has an alteration of substituting Pro at position 238 (EU numbering) with Asp) and then multiplying the result by 100, was shown as the relative binding activity value of each PD variant to each FcγR The horizontal axis shows relative values of the FcγRIIb-binding activity of each PD variant, and the vertical axis shows relative values of the FcγRIIa type R-binding activity of each PD variant (FIG. 33).

As a result, it was found that the FcγRIIb binding of eleven types of alterations were enhanced compared with the antibody before introducing alterations, and they have the effects of maintaining or enhancing FcγRIIa type R-binding. The activities of these eleven variants to bind FcγRIIb and FcγRIIa type R are summarized in Table 24. In the table, alteration refers to the alteration introduced into IL6R-F11 (SEQ ID NO: 161).

TABLE 24 RELATIVE RELATIVE BINDING BINDING ACTIVITY ACTIVITY VARIANT NAME ALTERATION TO FcγRIIb TO FcγRIIaR IL6R-F652/IL6R-L P238D 100 100 IL6R-PD042/IL6R-L P238D/L234W 106 240 IL6R-PD043/IL6R-L P238D/L234Y 112 175 IL6R-PD079/IL6R-L P238D/G237A 101 138 IL6R-PD080/IL6R-L P238D/G237D 127 222 IL6R-PD081/IL6R-L P238D/G237E 101 117 IL6R-PD082/IL6R-L P238D/G237F 108 380 IL6R-PD086/IL6R-L P238D/G237L 112 268 IL6R-PD087/IL6R-L P238D/G237M 109 196 IL6R-PD094/IL6R-L P238D/G237W 122 593 IL6R-PD095/IL6R-L P238D/G237Y 124 543 IL6R-PD097/IL6R-L P238D/S239D 139 844

FIG. 34 shows relative values for the FcγRIIb-binding activity of a variant obtained by additionally introducing the above eleven alterations into a variant carrying the P238D alteration, and relative values for the FcγRIIb-binding activity of a variant obtained by introducing the alterations into an Fc that does not contain the P238D. These eleven alterations enhanced the amount of FcγRIIb binding compared with before introduction when they were further introduced into the P238D variant. On the contrary, the effect of lowering FcγRIIb binding was observed for eight of those alterations except G237F. G237W, and S239D, when they were introduced into the variant that does not contain P238D (data not shown).

These results showed that, based on the effects of introducing alterations into a naturally-occurring IgG1, it is difficult to predict the effects of combining and introducing the same alterations into the variant containing the P238D alteration. In other words, it would not have been possible to discover these eight alterations identified this time without this investigation that the same alterations are combined and introduced into the variant containing the P238D alteration.

The results of measuring KD values of the variants indicated in Table 24 for FcγRIa, FcγRIIaR (allotype R131), FcγRIIaH (allotype H131), FcγRIIb, and FcγRIIIaV (allotype V158) by the method of Reference Example 2 are summarized in Table 25. In the table, alteration refers to the alteration introduced into IL6R-F11 (SEQ ID NO: 161). The template used for producing IL6R-F11, IL6R-G1d/IL6R-L, is indicated with an asterisk (*). Furthermore, KD (IIaR)/KD (IIb) and KD (IIaH)/KD (IIb) in the table respectively show the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of each variant for FcγRIIb, and the value obtained by dividing the KD value of each variant for FcγRIIaH by the KD value of each variant for FcγRIIb. KD (IIb) of the parent polypeptide/KD (IIb) of the variant refers to a value obtained by dividing the KD value of the parent polypeptide for FcγRIIb by the KD value of each variant for FcγRIIb. In addition, Table 25 shows KD values for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of each variant KD values for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide. Here, parent polypeptide refers to a variant which has IL6R-F11 (SEQ ID NO: 161) as the H chain. It was determined that due to weak binding of FcγR to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the gray-filled cells in Table 25 show values calculated by using Equation 2 of Reference Example 2.

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

Table 25 shows that all variants improved their affinity for FcγRIIb in comparison with IL6R-F11, and the range of improvement was 1.9 fold to 5.0 fold. The ratio of KD value of each variant for FcγRIIaR/KD value of each variant for FcγRIIb, and the ratio of KD value of each variant for FcγRIIaH/KD value of each variant for FcγRIIb represent an FcγRIIb-binding activity relative to the FcγRIIaR-binding activity and FcγRIIaH-binding activity, respectively. That is, these values show the degree of binding selectivity of each variant for FcγRIIb, and a larger value indicates a higher binding selectivity for FcγRIIb. For the parent polypeptide IL6R-F11/IL6R-L, the ratio of KD value for FcγRIIaR/KD value for FcγRIIb and the ratio of KD value for FcγRIIaH/KD value for FcγRIIb are both 0.7, and accordingly all variants in Table 25 showed improvement of binding selectivity for FcγRIIb in comparison with the parent polypeptide. When the KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant/KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant has equivalent or reduced binding compared with the binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide. Since this value was 0.7 to 5.0 for the variants obtained this time, one may say that binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the variants obtained this time was nearly the same or decreased in comparison with the parent polypeptide. These results showed that compared with the parent polypeptide, the variants obtained this time have maintained or decreased binding activities to FcγRIIa type R and type H and enhanced binding activity to FcγRIIb, and thus have improved selectivity for FcγRIIb. Furthermore, compared with IL6R-F11, all variants had lower affinity to FcγRIa and FcγRIIIaV.

TABLE 25

Reference Example 15 X-Ray Crystal Structure Analysis of a Complex Formed Between an Fc Containing P238D and an Extracellular Region of FcγRIIb

As indicated earlier in Reference Example 14, even though an alteration that is predicted from the analysis of naturally-occurring IgG1 antibodies to improve FcγRIIb-binding activity or selectivity for FcγRIIb is introduced into an Fc containing P238D, the FcγRIIb-binding activity was found to decrease, and the reason for this may be that the structure at the interacting interface between Fc and FcγRIIb is changed due to introduction of P238D. Therefore, to pursue the reason for this phenomena, the three-dimensional structure of the complex formed between an IgG1 Fc containing the P238D mutation (hereinafter, referred to as Fc (P238D)) and the extracellular region of FcγRIIb was elucidated by X-ray crystal structure analysis, and this was compared to the three-dimensional structure of the complex formed between the Fc of a naturally-occurring IgG (hereinafter, referred to as Fc (WT)) and the extracellular region of FcγRIIb, and the binding modes were compared. Multiple reports have been made on the three-dimensional structure of a complex formed between an Fc and an FcγR extracellular region; and the three-dimensional structures of the Fc (WT)/FcγRIIIb extracellular region complex (Nature (2000) 400, 267-273; J. Biol. Chem. (2011) 276, 16469-16477), the Fc (WT)/FcγRIIIa extracellular region complex (Proc. Natl. Acad. Sci. USA (2011) 108, 12669-126674), and the Fc (WT)/FcγRIIa extracellular region complex (J. Immunol. (2011) 187, 3208-3217) have been analyzed. While the three-dimensional structure of the Fc (WT)/FcγRIIb extracellular region complex has not been analyzed, the three-dimensional structure of a complex formed with Fc (WT) is known for FcγRIIa, and the extracellular regions of FcγRIIa and FcγRIIb match 93% in amino acid sequence and have very high homology. Thus, the three-dimensional structure of the Fc (WT)/FcγRIIb extracellular region complex was predicted by modeling using the crystal structure of the Fc (WT)/FcγRIIa extracellular region complex.

The three-dimensional structure of the Fc (P238D)/FcγRIIb extracellular region complex was determined by X-ray crystal structure analysis at 2.6 Å resolution. The structure obtained as a result of this analysis is shown in FIG. 35. The FcγRIIb extracellular region is bound between two Fc CH2 domains, and this was similar to the three-dimensional structures of complexes formed between Fc (WT) and the respective extracellular region of FcγRIIIa, FcγRIIIb, or FcγRIIa analyzed so far. Next, for detailed comparison, the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex and the model structure of the Fc (WT)/FcγRIIb extracellular region complex were superimposed by the least squares fitting based on the Cα atom pair distances with respect to the FcγRIIb extracellular region and the Fc CH2 domain A (FIG. 36). In that case, the degree of overlap between Fc CH2 domains B was not satisfactory, and conformational differences were found in this portion. Furthermore, using the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex and the model structure of the Fc (WT)/FcγRIIb extracellular region complex, pairs of atoms that have a distance of 3.7 Å or less between the FcγRIIb extracellular region and Fc CH2 domain B were extracted and compared in order to compare the interatomic interaction between FcγRIIb and Fc (WT) CH2 domain B with the interatomic interaction between FcγRIIb and Fc (P238D) CH2 domain B. As shown in Table 26, the interatomic interactions between Fc CH2 domain B and FcγRIIb in Fc (P238D) and Fc (WT) did not match.

TABLE 26 Fc (P238D) CH2 DOMAIN B Fc (WT) CH2 DOMAIN B INTERACTION PARTNER INTERACTION PARTNER (DISTANCE BETWEEN (DISTANCE BETWEEN FcγRIIb ATOM ATOMS, Å) ATOMS, Å) Val 116 CG2 Asp 265 OD2 (3.47) Gly 237 O (3.65) Ser 126 OG Ser 298 N (3.31) Ser 298 CB (3.32) Tyr 296 O (3.05) Lys 128 CA Ser 298 OG (3.50) Phe 129 CB Ser 298 O (3.36) Phe 129 CD2 Asn 297 CB (3.50) Asn 297 CG (3.43) Lys 128 C Ser 298 O (3.47) Phe 129 N Ser 298 OG (3.30) Phe 129 O Ser 267 OG (3.54) Arg 131 CB Val 266 O (3.02) Arg 131 CG Val 266 O (3.22) Arg 131 CD Val 266 CG1 (3.45) Val 266 C (3.55) Val 266 O (3.10) Arg 131 NE Ala 327 O (3.60) Val 266 C (3.66) Val 266 O (3.01) Val 266 N (3.49) Arg 131 CZ Asp 270 CG (3.64) Val 266 N (3.13) Asp 270 OD2 (3.22) Asp 270 OD1 (3.27) Ala 327 CB (3.63) Arg 131 NH1 Asp 270 CG (3.19) Val 266 CG1 (3.47) Asp 270 OD2 (2.83) Val 266 N (3.43) Asp 270 OD1 (2.99) Thr 299 OG1 (3.66) Ser 267 CB (3.56) Ser 298 O (3.11) Arg 131 NH2 Asp 270 CG (3.20) Asp 265 CA (3.16) Asp 270 OD2 (2.80) Val 266 N (3.37) Asp 270 OD1 (2.87) Ala 327 CB (3.66) Tyr 157 CE1 Leu 234 CG (3.64) Leu 234 CD1 (3.61) Tyr 157 OH Gly 236 O (3.62) Leu 234 CA (3.48) Leu 234 CG (3.45)

Furthermore, the detailed structures around P238D were compared by superposing the X-ray crystal structure of Fc (P238D)/FcγRIIb extracellular region complex on the model structure of the Fc (WT)/FcγRIIb extracellular region complex using the least squares method based on the Cα atomic distance between Fc CH2 domains A and B alone. As the position of the amino acid residue at position 238 (EU numbering), i.e., a mutagenesis position of Fc (P238D), is altered from Fc (WT), the loop structure around the amino acid residue at position 238 following the hinge region is found to be different between Fc (P238D) and Fc (WT) (FIG. 37). Pro at position 238 (EU numbering) is originally located inside Fc (WT), forming a hydrophobic core with residues around position 238. However, if Pro at position 238 (EU numbering) is altered to highly hydrophilic and charged Asp, the presence of the altered Asp residue in a hydrophobic core is energetically disadvantageous in terms of desolvation. Therefore, in Fc (P238D), to cancel this energetically disadvantageous situation, the amino acid residue at position 238 (EU numbering) may have changed its orientation to face the solvent side, and this may have caused the change in the loop structure near the amino acid residue at position 238. Furthermore, since this loop is not far from the hinge region crosslinked by an S—S bond, its structural change will not be limited to a local change, and will affect the relative positioning of the Fc CH2 domain A and domain B. As a result, the interatomic interactions between FcγRIIb and Fc CH2 domain B have been changed. Therefore, predicted effects could not be observed when alterations that improve selectivity and binding activity towards FcγRIIb in a naturally-occurring IgG were combined with an Fc containing the P238D alteration.

Furthermore, as a result of structural changes due to introduction of P238D in Fc CH2 domain A, a hydrogen bond has been found between the main chain of Gly at position 237 (EU numbering), which is adjacent to P238D mutated, and Tyr at position 160 in FcγRIIb (FIG. 38). The residue in FcγRIIa that corresponds to this Tyr 160 is Phe; and when the binding is to FcγRIIa, this hydrogen bond is not formed. Considering that the amino acid at position 160 is one of the few differences between FcγRIIa and FcγRIIb at the interface of interaction with Fc, the presence of this hydrogen bond which is specific to FcγRIIb is presumed to have led to improvement of FcγRIIb-binding activity and decrease of FcγRIIa-binding activity in Fc (P238D), and improvement of its selectivity. Furthermore, in Fc CH2 domain B, an electrostatic interaction is observed between Asp at position 270 (EU numbering) and Arg at position 131 in FcγRIIb (FIG. 39). In FcγRIIa type H, which is one of the allotypes of FcγRIIa, the residue corresponding to Arg at position 131 of FcγRIIb is His, and therefore cannot form this electrostatic interaction. This can explain why the Fc (P238D)-binding activity is lowered in FcγRIIa type H compared with FcγRIIa type R Observations based on such results of X-ray crystal structure analysis showed that the change of the loop structure beside P238D due to P238D introduction and the accompanying change in the relative domain positioning could cause formation of new interactions which is not found in the binding of the naturally-occurring IgG and FcγR, and this could lead to a selective binding profile of P238D variants for FcγRIIb.

[Expression and Purification of Fc (P238D)]

An Fc containing the P238D alteration was prepared as follows. First, Cys at position 220 (EU numbering) of hIL6R-IgG1-v1 (SEQ ID NO: 163) was substituted with Ser. Then, genetic sequence of Fc (P238D) from Glu at position 236 (EU numbering) to its C terminal was cloned by PCR. Using this cloned genetic sequence, production of expression vectors, and expression and purification of Fc (P238D) were carried out according to the method of Reference Example 1. Cys at position 220 (EU numbering) forms a disulfide bond with Cys of the L chain in general IgG1. The L chain is not co-expressed when Fc alone is prepared, and therefore, the Cys residue was substituted with Ser to avoid formation of unnecessary disulfide bonds.

[Expression and Purification of the FcγRIIb Extracellular Region]

The FcγRIIb extracellular region was prepared according to the method of Reference Example 2.

[Purification of the Fc (P238D)/FcγRIIb Extracellular Region Complex]

To 2 mg of the FcγRIIb extracellular region sample obtained for use in crystallization, 0.29 mg of Endo F1 (Protein Science (1996) 5: 2617-2622) expressed and purified from Escherichia coli as a glutathione S-transferase fusion protein was added. This was allowed to remain at room temperature for three days in 0.1 M Bis-Tris buffer at pH 6.5, and the N-linked oligosaccharide was cleaved, except for N-acetylglucosamine directly bound to Asn of the FcγRIIb extracellular region. Next, the FcγRIIb extracellular region sample subjected to carbohydrate cleavage treatment, which was concentrated by ultrafiltration with 5000 MWCO, was purified by gel filtration chromatography (Superdex200) 10/300) using a column equilibrated in 20 mM HEPS at pH 7.5 containing 0.05 M NaCl. Furthermore, to the obtained carbohydrate-cleaved FcγRIIb extracellular region fraction, Fc (P238D) was added so that the molar ratio of the FcγRIIb extracellular region would be present in slight excess. The mixture concentrated by ultrafiltration with 10,000 MWCO was subjected to purification by gel filtration chromatography (Superdex200 10/300) using a column equilibrated in 20 mM HEPS at pH 7.5 containing 0.05 M NaCl. Thus, a sample of the Fc (P238D)/FcγRIIb extracellular region complex was obtained.

[Crystallization of the Fc (P238D)/FcγRIIb Extracellular Region Complex]

Using the sample of the Fc (P238D)/FcγRIIb extracellular region complex which was concentrated to approximately 10 mg/mL by ultrafiltration with 10,000 MWCO, crystallization of the complex was carried out by the sitting drop vapor diffusion method. Hydra II Plus One (MATRIX) was used for crystallization; and for a reservoir solution containing 100 mM Bis-Tris pH 6.5, 17% PEG3350, 0.2 M ammonium acetate, and 2.7% (w/v) D-Galactose, a crystallization drop was produced by mixing at a ratio of reservoir solution:crystallization sample=0.2 μL:0.2 μL. The crystallization drop after sealing was allowed to remain at 20° C., and thus thin plate-like crystals were obtained.

[Measurement of X-Ray Diffraction Data from an Fc (P238D)/FcγRIIb Extracellular Region Complex Crystal]

One of the obtained single crystals of the Fc (P238D)/FcγRIIb extracellular region complex was soaked into a solution of 100 mM Bis-Tris pH 6.5, 20% PEG3350, ammonium acetate, 2.7% (w/v) D-Galactose, 22.5% (v/v) ethylene glycol. The single crystal was fished out of the solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. Then, the X-ray diffraction data of the crystal was measured at synchrotron radiation facility Photon Factory BL-1A in High Energy Accelerator Research Organization. During the measurement, the crystal was constantly placed in a nitrogen stream at −178° C. to maintain in a frozen state, and a total of 225 X-ray diffraction images were collected using Quantum 270 CCD detector (ADSC) attached to a beam line with rotating the crystal 0.8° at a time. Determination of cell parameters, indexing of diffraction spots, and diffraction data processing from the obtained diffraction images were performed using the Xia2 program (CCP4 Software Suite), XDS Package (Walfgang Kabsch) and Scala (CCP4 Software Suite); and finally, diffraction intensity data of the crystal up to 2.46 Å resolution was obtained. The crystal belongs to the space group P21, and has the following cell parameters; a=48.85 Å, b=76.01 Å, c=115.09 Å, α=90°, β=100.70°, γ=90°.

[X-Ray Crystal Structure Analysis of the Fc (P238D)/FcγRIIb Extracellular Region Complex]

Crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex was determined by the molecular replacement method using the program Phaser (CCP4 Software Suite). From the size of the obtained crystal lattice and the molecular weight of the Fc (P238D)/FcγRIIb extracellular region complex, the number of complexes in the asymmetric unit was predicted to be one. From the structural coordinates of PDB code: 3SGJ which is the crystal structure of the Fc (WT)/FcγRIIIa extracellular region complex, the amino acid residue portions of the A chain positions 239-340 and the B chain positions 239-340 were taken out as separate coordinates, and they were set respectively as models for searching the Fc CH2 domains. The amino acid residue portions of the A chain positions 341-444 and the B chain positions 341-443 were taken out as a single set of coordinates from the same structural coordinates of PDB code: 3SGJ; and this was set as a model for searching the Fc CH3 domains. Finally, from the structural coordinates of PDB code: 2FCB which is a crystal structure of the FcγRIIb extracellular region, the amino acid residue portions of the A chain positions 6-178 was taken out and set as a model for searching the FcγRIIb extracellular region. The orientation and position of each search model in the crystal lattice were determined in the order of Fc CH3 domain, FcγRIIb extracellular region, and Fc CH2 domain, based on the rotation function and translation function to obtain the initial model for the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex. When rigid body refinement which moves the two Fc CH2 domains, the two Fc CH3 domains, and the FcγRIIb extracellular region was performed on the obtained initial model, the crystallographic reliability factor, R value became 40.4%, and the Free R value became 41.9% to diffraction intensity data from 25 Å to 3.0 Å at this point. Furthermore, structural refinement using the program Refmac5 (CCP4 Software Suite), and revision of the model to observe the electron density maps whose coefficient have 2Fo-Fc or Fo-Fc, which are calculated based on the experimentally determined structural factor Fo, the calculated structural factor Fc and the calculated phase using the model, was carried out by the Coot program (Paul Emsley). Model refinement was carried out by repeating these steps. Finally, as a result of incorporation of water molecules into the model based on the electron density maps which use 2Fo-Fc or Fo-Fc as the coefficient, and the following refinement, the crystallographic reliability factor, R values and the Free R value of the model containing 4846 non-hydrogen atoms became 23.7% and 27.6% to 24291 diffraction intensity data from 25 Å to 2.6 Å resolution, respectively.

[Production of a Model Structure of the Fc (WT)/FcγRIIb Extracellular Region Complex]

Based on the structural coordinates of PDB code: 3RY6 which is a crystal structure of the Fc (WT)/FcγRIIa extracellular region complex, the Build Mutants function of the Discovery Studio 3.1 program (Accelrys) was used to introduce mutations to match the amino acid sequence of FcγRIIb into FcγRIIa in this structural coordinates. In that case, the Optimization Level was set to High, Cut Radius was set to 4.5, five models were generated, and the one with the best energy score from among them was set as the model structure for the Fc (WT)/FcγRIIb extracellular region complex.

Reference Example 16 Analysis of FcγR Binding of Fc Variants Whose Alteration Sites were Determined Based on Crystal Structures

Based on the results of X-ray crystal structure analysis on the complex formed between Fc (P238D) and the FcγRIIb extracellular region obtained in Reference Example 15, variants were constructed by comprehensively introducing alterations into sites on the altered Fc having substitution of Pro at position 238 (EU numbering) with Asp that were predicted to affect interaction with FcγRIIb (residues of positions 233, 240, 241, 263, 265, 266, 267, 268, 271, 273, 295, 296, 298, 300, 323, 325, 326, 327, 328, 330, 332, and 334 (EU numbering)), and whether combinations of alterations that further enhance FcγRIIb binding in addition to the P238D alteration can be obtained, was examined.

IL6R-B3 (SEQ ID NO: 164) was produced by introducing into IL6R-G1d (SEQ ID NO: 156), the alteration produced by substituting Lys at position 439 (EU numbering) with Glu. Next, IL6R-BF648 was produced by introducing into IL6R-B3, the alteration produced by substituting Pro at position 238 (EU numbering) with Asp. IL6R-L (SEQ ID NO: 155) was utilized as the common antibody L chain. These antibody variants expressed were purified according to the method of Reference Example 1. The binding of these antibody variants to each of the FcγRs (FcγRIa, FcγRIIa type H, FcγRIa type R, FcγRIIb, and FcγRIIIa type V) was comprehensively evaluated by the method of Reference Example 2.

A figure was produced according to the following method to show the results of analyzing the interactions with the respective FcγRs. The value for the amount of binding of each variant to each FcγR was divided by the value for the amount of binding of the pre-altered control antibody (IL6R-BF648/IL6R-L, alteration by substituting Pro at position 238 (EU numbering) with Asp) to each FcγR, and the obtained was then multiplied by 100 and shown as the relative binding activity value of each variant to each FcγR. The horizontal axis shows the relative binding activity value of each variant to FcγRIIb, and the vertical axis shows the relative binding activity value of each variant to FcγRIIa type R (FIG. 40).

As shown in FIG. 40, the results show that of all the alterations, 24 types of alterations were found to maintain or enhance FcγRIIb binding in comparison with the pre-altered antibody. The binding of these variants to each of the FcγRs are shown in Table 27. In the table, alteration refers to the alteration introduced into IL6R-B3 (SEQ ID NO: 164). The template used for producing IL6R-B3, IL6R-G1d/IL6R-L, is indicated with an asterisk (*).

TABLE 27 RELATIVE BINDING VARIANT NAME ALTERATION FcγRIa FcγRIIaR FcγRIIaH FcγRIIb FcγRIIIa IL6R- * 140 650 1670 62 3348 G1d/IL6R-L IL6R-B3/IL6R-L 145 625 1601 58 3264 IL6R- P238D 100 100 100 100 100 BF648/IL6R-L IL6R- P238D/E233D 118 103 147 116 147 2B002/IL6R-L IL6R- P238D/S267A 121 197 128 110 138 BP100/IL6R-L IL6R- P238D/S267Q 104 165 66 106 86 BP102/IL6R-L IL6R- P238D/S267V 56 163 69 107 77 BP103/IL6R-L IL6R- P238D/H268D 127 150 110 116 127 BP106/IL6R-L IL6R- P238D/H268E 123 147 114 118 129 BP107/IL6R-L IL6R- P238D/H268N 105 128 127 101 127 BP110/IL6R-L IL6R- P238D/P271G 119 340 113 157 102 BP112/IL6R-L IL6R- P238D/Y296D 95 87 37 103 96 2B128/IL6R-L IL6R- P238D/V323I 73 92 83 104 94 2B169/IL6R-L IL6R- P238D/V323L 116 117 115 113 122 2B171/IL6R-L IL6R- P238D/V323M 140 244 179 132 144 2B172/IL6R-L IL6R- P238D/K326A 117 159 103 119 102 BP136/IL6R-L IL6R- P238D/K326D 124 166 96 118 105 BP117/IL6R-L IL6R- P238D/K326E 125 175 92 114 103 BP120/IL6R-L IL6R- P238D/K326L 113 167 132 103 146 BP126/IL6R-L IL6R- P238D/K326M 117 181 133 110 145 BP119/IL6R-L IL6R- P238D/K326N 98 103 97 106 102 BP142/IL6R-L IL6R- P238D/K326Q 118 155 135 113 157 BP121/IL6R-L IL6R- P238D/K326S 101 132 128 104 144 BP118/IL6R-L IL6R- P238D/K326T 110 126 110 108 114 BP116/IL6R-L IL6R- P238D/A330K 52 101 108 119 120 BP911/IL6R-L IL6R- P238D/A330M 106 101 89 105 91 BP078/IL6R-L IL6R- P238D/A330R 60 81 93 103 97 BP912/IL6R-L

The results of measuring KD values of the variants shown in Table 27 for FcγRIa. FcγRIIaR, FcγRIIaH, FcγRIb, and FcγRIIIa V by the method of Reference Example 2 are summarized in Table 28. In the table, alteration refers to the alteration introduced into IL6R-B3 (SEQ ID NO: 164). The template used for producing IL6R-B3, IL6R-G1d/IL6R-L, is indicated with an asterisk (*). Furthermore, KD (IIaR)/KD (IIb) and KD (IIaH)/KD (IIb) in the table respectively represent the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of each variant for FcγRIIb, and the value obtained by dividing the KD value of each variant for FcγRIIaH by the KD value of each variant for FcγRIIb. KD (IIb) of the parent polypeptide/KD (IIb) of the altered polypeptide refers to the value obtained by dividing the KD value of the parent polypeptide for FcγRIIb by the KD value of each variant for FcγRIIb. In addition, the KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of each variant KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide are shown in Table 28. Here, parent polypeptide refers to the variant which has IL6R-B3 (SEQ ID NO: 164) as the H chain. It was determined that due to weak binding of FcγR to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the gray-filled cells in Table 28 show values calculated by using Equation 2 of Reference Example 2.

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

TABLE 28

Table 28 shows that in comparison with IL6R-B3, all variants showed improvement of affinity for FcγRIIb, and the range of improvement was 2.1 fold to 9.7 fold. The ratio of KD value of each variant for FcγRIIaR/KD value of each variant for FcγRIIb, and the ratio of KD value of each variant for FcγRIIaH/KD value of each variant for FcγRIIb represent an FcγRIIb-binding activity relative to the FcγRIIaR-binding activity and FcγRIIaH-binding activity, respectively. That is, these values show the degree of binding selectivity of each variant for FcγRIIb, and a greater value indicates a higher binding selectivity for FcγRIIb. Since the ratio of KD value for FcγRIIaR/KD value for FcγRIIb, and the ratio of KD value for FcγRIIaH/KD value for FcγRIIb in the parent polypeptide IL6R-B3/IL6R-L were 0.3 and 0.2, respectively, all variants in Table 28 showed improvement of binding selectivity for FcγRIIb in comparison with the parent polypeptide. When the KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant/KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant has equivalent or decreased binding compared with the binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide. Since this value was 4.6 to 34.0 for the variants obtained this time, one may say that in comparison with the parent polypeptide, the variants obtained this time had reduced binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities. These results showed that compared with the parent polypeptide, the variants obtained this time have maintained or decreased FcγRIIa type R- and type H-binding activities, enhanced FcγRIIb-binding activity, and improved selectivity for FcγRIIb. Furthermore, compared with IL6R-B3, all variants had lower affinity to FcγRIa and Fc-RIIIaV.

With regard to the promising variants among the obtained combination variants, the factors leading to their effects were studied using the crystal structure. FIG. 41 shows the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex. In this figure, the H chain positioned on the left side is Fc Chain A, and the H chain positioned on the right side is Fc Chain B. Here, one can see that the site at position 233 (EU numbering) in Fc Chain A is located near Lys at position 113 of FcγRIIb. However, in this crystal structure, the E233 side chain is in a condition of considerably high mobility, and its electron density is not well observed. Therefore, the alteration produced by substituting Glu at position 233 (EU numbering) with Asp leads to decrease in the degree of freedom of the side chain since the side chain becomes one carbon shorter. As a result, the entropy loss when forming an interaction with Lys at position 113 of FcγRIIb may be decreased, and consequently this is speculated to contribute to improvement of binding free energy.

Similarly, FIG. 42 shows the environment near the site at position 330 (EU numbering) in the structure of the Fc (P238D)/FcγRIIb extracellular region complex. This figure shows that the environment around the site at position 330 (EU numbering) of Fc Chain A of Fc (P238D) is a hydrophilic environment composed of Ser at position 85, Glu at position 86, Lys at position 163, and such of FcγRIIb. Therefore, the alteration produced by substituting Ala at position 330 (EU numbering) with Lys or Arg is speculated to contribute to strengthening the interaction with Ser at position 85 or Glu at position 86 in FcγRIIb.

FIG. 43 depicts the structures of Pro at position 271 (EU numbering) of Fc Chain B after superimposing the crystal structures of the Fc (P238D)/FcγRIIb extracellular region complex and the Fc (WT)/FcγRIIIa extracellular region complex by the least squares fitting based on the Cα atom pair distances with respect to Fc Chain B. These two structures match well, but have different three-dimensional structures of Pro at position 271 (EU numbering). When the weak electron density around this area in the crystal structure of the Fc (P238D)/FcγRIIb extracellular region complex is also taken into consideration, it is suggested that there is possibility that Pro at position 271 (EU numbering) in Fc (P238D)/FcγRIIb causes a large strain on the structure, thus disturbing the loop structure to attain an optimal structure. Therefore, the alteration produced by substituting Pro at position 271 (EU numbering) with Gly is speculated to give flexibility to this loop structure, and contribute to enhancement of binding by reducing the energetic barrier for attaining an optimum structure when interacting with FcγRIIb.

Reference Example 17 Examination of the Combinatorial Effect of Alterations that Enhance FcγRIIb Binding when Combined with P238D

Of the alterations obtained in Reference Examples 14 and 16, those that showed effects of enhancing FcγRIIb binding or maintaining FcγRIIb binding and suppressing binding to other FcγRs were combined with each other, and its effect was examined.

Particularly good alterations selected from Tables 24 and 28 were introduced into the antibody H chain IL6R-BF648 in a similar manner to the method of Reference Example 16. IL6R-L was utilized as the antibody L chain, and the expressed antibodies were purified according to the method of Reference Example 1. The binding to each of the FcγRs (FcγRIa, FcγRIIa H type, FcγRIIa R type, FcγRIIb, and FcγRIIIa V type) was comprehensively evaluated by the method of Reference Example 2.

According to the following method, relative binding activities were calculated for the results of analyzing interactions with the respective FcγRs. The value for the amount of binding of each variant to each FcγR was divided by the value for the amount of binding of the pre-altered control antibody (IL6R-BF648/IL6R-L with substitution of Pro at position 238 (EU numbering) with Asp) to each FcγR, and multiplied by 100; and then the value was shown as the relative binding activity value of each variant to each FcγR (Tables 29-1 to 29-2). In the table, alteration refers to the alteration introduced into IL6R-B3 (SEQ ID NO: 164). The template used for producing IL6R-B3, IL6R-G1d/IL6R-L, is indicated with an asterisk (*).

TABLE 29-1 VARIANT RELATIVE BINDING ACTIVITY NAME ALTERATION FcgRIa FcgRIIaR FcgRIIaH FcgRIIb FcgRIIIaV IL6R-G1d/IL6R-L * 140 650 1670 52 3348 IL6R-B3/IL6R-L 145 625 1601 58 3264 IL6R-BF648/IL6R-L P238D 100 100 100 100 100 IL6R-2B253/IL6R-L E233D/P238D/V323M 155 280 207 156 126 IL6R-2B261/IL6R-L E233D/P238D/Y296D 100 94 91 115 87 IL6R-BP082/IL6R-L E233D/P238D/A330K 74 126 106 136 87 IL6R-BP083/IL6R-L P238D/Y296D/A330K 50 87 91 122 107 IL6R-BP084/IL6R-L P238D/V323M/A330K 109 203 162 141 106 IL6R-BP085/IL6R-L G237D/P238D/A330K 19 279 158 152 104 IL6R-BP086/IL6R-L P238D/K326A/A330K 72 155 116 137 123 IL6R-BP087/IL6R-L L234Y/P238D/A330K 33 163 179 137 158 IL6R-BP088/IL6R-L G237D/P238D/K326A/A330K 25 377 166 161 122 IL6R-BP089/IL6R-L L234Y/P238D/K326A/A330K 43 222 186 147 136 IL6R-BP129/IL6R-L E233D/P238D/Y296D/A330K 68 111 96 138 95 IL6R-BP130/IL6R-L E233D/P238D/V323M/A330K 104 272 224 160 115 IL6R-BP131/IL6R-L E233D/G237D/P238D/A330K 33 384 253 160 116 IL6R-BP132/IL6R-L E233D/P238D/K326A/A330K 91 191 130 150 120 IL6R-BP133/IL6R-L E233D/L234Y/P238D/A330K 41 174 151 137 114 IL6R-BP143/IL6R-L L234Y/P238D/K326A 88 238 143 133 114 IL6R-BP144/IL6R-L G237D/P238D/K326A 64 204 108 121 126 IL6R-BP145/IL6R-L L234Y/G237D/P238D 41 350 224 152 153 IL6R-BP146/IL6R-L L234Y/G237D/P238D/K326A 50 445 203 156 180 IL6R-BP147/IL6R-L L234Y/G237D/P236D/K326A/A330K 24 650 532 177 209 IL6R-BP148/IL6R-L E233D/L234Y/G237D/P238D/K326A/A330K 33 603 462 176 227 IL6R-BP149/IL6R-L E233D/L234Y/G237D/P238D/Y296D/K326A/A330K 29 539 401 173 186 IL6R-BP150/IL6R-L L234Y/G237D/P238D/K326A/A330K 30 757 770 183 204 IL6R-BP151/IL6R-L E233D/L234Y/G237D/P238D/K326A/A330K 39 705 521 180 221 IL6R-BP152/IL6R-L E233D/L234Y/G237D/P238D/Y296D/K326A/A330R 34 636 546 178 146 IL6R-BP176/IL6R-L E233D/P238D/K326D/A330K 102 201 128 147 131 IL6R-BP177/IL6R-L E233D/L234Y/G237D/P238D/P271G/K326D/A330K 57 691 409 177 166 IL6R-BP178/IL6R-L E233D/G237D/P238D/P271G/A330K 51 653 259 179 110 IL6R-BP179/IL6R-L G237F/P238D/P271G/K326A/A330K 39 870 226 177 126 IL6R-BP180/IL6R-L G237D/P238D/P271G/A330K 39 602 203 179 100

Table 29-2 is a continuation table of Table 29-1.

TABLE 29-2 IL6R-BP181/IL6R-L E233D/P238D/P271G/K326A/A330K 108 352 150 170 122 IL6R-BP182/IL6R-L E233D/P238D/P271G/Y296D/A330K 95 413 139 173 120 IL6R-BP183/IL6R-L E233D/L234Y/P238D/P271G/K326A/A330K 83 423 191 164 113 IL6R-BP184/IL6R-L E233D/P236D/P271G/A330K 96 436 131 171 106 IL6R-BP185/IL6R-L E233D/L234Y/G237D/P238D/P271G/K326A/A330K 47 670 446 179 191 IL6R-BP186/IL6R-L E233D/L234Y/G237D/P238D/P271G/Y296D/K326A/A330K 43 614 368 175 143 IL6R-BP187/IL6R-L L234Y/P238D/P271G/K326A/A330K 68 387 205 157 124 IL6R-BP188/IL6R-L E233D/G237D/P238D/H268D/P271G/A330K 74 636 234 179 121 IL6R-BP189/IL6R-L G237D/P238D/H268D/P271G/K326A/A330K 56 557 163 177 141 IL6R-BP190/IL6R-L G237D/P238D/H268D/P271G/A330K 50 615 224 181 155 IL6R-BP191/IL6R-L E233D/P238D/H268D/P271G/K326A/A330K 125 382 145 170 142 IL6R-BP192/IL6R-L E233D/P238D/H268D/P271G/Y296D/A330K 109 406 122 172 118 IL6R-BP193/IL6R-L E233D/P238D/H268D/P271G/A330K 113 449 154 173 135 IL6R-BP194/IL6R-L E233D/L234Y/G237D/P238D/H268D/P271G/K326A/A330K 69 672 395 178 249 IL6R-BP195/IL6R-L E233D/L234Y/G237D/P238D/H268D/P271G/Y296D/K326A/A330K 66 651 344 181 221 IL6R-BP196/IL6R-L L234Y/P238D/H268D/P271G/K326A/A330K 89 402 195 157 137 IL6R-BP197/IL6R-L E233D/L234Y/G237D/P238D/H268D/P271G/Y296D/K326D/A330K 71 642 294 179 206 IL6R-BP198/IL6R-L E233D/L234Y/P238D/H268D/P271G/K326A/A330K 104 449 188 164 157 IL6R-BP199/IL6R-L E233D/P238D/K326D/A330K 112 172 116 144 103 IL6R-BP200/IL6R-L E233D/L234Y/G237D/P238D/P271G/K326A/A330R 60 754 517 188 164 IL6R-BP201/IL6R-L E233D/G237D/P238D/P271G/A330R 57 696 359 166 121 IL6R-BP202/IL6R-L G237D/P238D/P271G/K326A/A330R 43 615 285 185 108 IL6R-BP203/IL6R-L G237D/P238D/P271G/A330R 35 637 255 165 66 IL6R-BP204/IL6R-L E233D/P238D/P271G/K326A/A330R 110 301 137 165 121 IL6R-BP205/IL6R-L E233D/P238D/P271G/Y396D/A330R 97 335 106 167 93 IL6R-BP206/IL6R-L E233D/P238D/P271G/A330R 101 362 123 166 92 IL6R-BP207/IL6R-L E233D/P238D/A330R 74 103 103 124 97 IL6R-BP208/IL6R-L E233D/G237D/P238D/H268D/P271G/A330R 81 690 310 188 118 IL6R-BP209/IL6R-L G237D/P238D/H268D/P271G/K326A/A330R 65 625 267 186 153 IL6R-BP210/IL6R-L G237D/P238D/H268D/P271G/A330R 57 661 279 187 135 IL6R-BP211/IL6R-L E233D/P238D/H268D/P271G/K326A/A330R 128 312 111 165 87 IL6R-BP212/IL6R-L E233D/P238D/H268D/P271G/Y296D/A330R 117 363 135 173 122 IL6R-BP213/IL6R-L E233D/P238D/H268D/P271G/A330R 118 382 123 169 100 IL6R-BP214/IL6R-L E233D/L234Y/G237D/P238D/Y296D/K326D/A330K 36 498 285 174 165

The results of measuring KD values of the variants shown in Tables 29-1 and 29-2 for FcγRIa, FcγRIIaR, FcγRIIaH, FcγRIIb, and FcγRIIIaV by the method of Reference Example 2 are summarized in Tables 30-1 and 30-2. In the table, alteration refers to the alteration introduced into IL6R-B3 (SEQ ID NO: 164). The template used for producing IL6R-B3, IL6R-G1d/IL6R-L, is indicated with an asterisk (*). Furthermore, KD (IIaR)/KD (IIb) and KD (IIaH)/KD (IIb) in the table respectively represent the value obtained by dividing the KD value of the variant for FcγRIIaR by the KD value of the variant for FcγRIIb, and the value obtained by dividing the KD value of the variant for FcγRIIaH by the KD value of each variant for FcγRIIb. KD (IIb) of the parent polypeptide/KD (IIb) of the altered polypeptide refers to the value obtained by dividing the KD value of the parent polypeptide for FcγRIIb by the KD value of each variant for FcγRIIb. In addition, the KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of each variant/KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide are shown in Tables 30-1 and 30-2. Here, parent polypeptide refers to the variant which has IL6R-B3 (SEQ ID NO: 164) as the H chain. It was determined that due to weak binding of FcγR to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the values of gray-filled cells in Tables 30-1 and 30-2 show values calculated by using Equation 2 of Reference Example 2.

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

Tables 30-1 and 30-2 show that in comparison with IL6R-B3, all variants showed improvement of affinity for FcγRIIb, and the range of improvement was 3.0 fold to 99.0 fold. The ratio of KD value of each variant for FcγRIIaR/KD value of each variant for FcγRIIb, and the ratio of KD value of each variant for FcγRIIaH/KD value of each variant for FcγRIIb represent an FcγRIIb-binding activity relative to the FcγRIIaR-binding activity and FcγRIIaH-binding activity, respectively. That is, those values show the degree of binding selectivity of each variant for FcγRIIb, and a greater value indicates a higher binding selectivity for FcγRIIb. Since the ratio of KD value for FcγRIIaR/KD value for FcγRIIb, and the ratio of KD value for FcγRIIaH/KD value for FcγRIIb of the parent polypeptide IL6R-B3/IL6R-L were 0.3 and 0.2, respectively, all variants in Tables 30-1 and 30-2 showed improvement of binding selectivity for FcγRIIIb in comparison with the parent polypeptide. When the KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant/KD value for the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of a variant has equivalent or decreased binding compared with the binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the parent polypeptide. Since this value was 0.7 to 29.9 for the variants obtained this time, one may say that binding by the stronger of the FcγRIIaR- and FcγRIIaH-binding activities of the variants obtained this time was nearly equivalent or decreased compared with that of the parent polypeptide. These results showed that compared with the parent polypeptide, the variants obtained this time have maintained or decreased FcγRIIa type R- and type H-binding activities, enhanced FcγRIIb-binding activity, and improved selectivity for FcγRIIb. Furthermore, compared with IL6R-B3, all variants had lower affinity for FcγRIa and FcγRIIIaV.

TABLE 30-1

Table 30-2 is a continuation table of Table 30-1.

TABLE 30-2

Reference Example 18 Preparation of Variants with Enhanced FcγRIIb Binding

As shown in Reference Example 13, when enhancing the FcγRIIb binding, it is preferable that the FcγRIIb binding is enhanced while maximally suppressing the binding to other activating FcγRs. Thus, the present inventors additionally produced variants with enhanced FcγRIIb binding or improved selectivity to FcγRIIb by combining alterations that enhance the FcγRIIb binding or improve the selectivity to FcγRIIb. Specifically, the alterations described in Reference Examples 14, 16, and 17 which were found to be effective when combined with alteration P238D, were combined with one another, on the basis of the P238D alteration which showed the excellent effect to enhance the FcγRIIb binding and to improve the selectivity to FcγRIIb.

Variants were produced by combining the Fc regions of IL6R-G1d (SEQ ID NO: 156) and IL6R-B3 (SEQ ID NO: 164) with alterations E233D, L234Y, G237D, S267Q, H268D, P271G, Y296D, K326D, K326A, A330R, and A330K described in Reference Examples 14, 16, and 17 which were found to be effective when combined with alteration P238D. Using IL6R-L (SEQ ID NO: 155) as the antibody L chain, antibodies comprising the above-described variants in the heavy chain were expressed and purified according to the method described in Reference Example 1. The resulting variants were respectively assessed for the binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR. FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2.

The KD value of each variant to each FcγR is shown in Table 31. “Alteration” refers to an alteration introduced into IL6R-B3 (SEQ ID NO: 164). IL6R-B3/IL6R-L which is used as the template to produce each variant is indicated by asterisk (*). KD (IIaR)/KD (IIb) in the table shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of each variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb. KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. Meanwhile, KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIaR by the KD value of each variant for FcγRIIaR. In Table 31, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

TABLE 31

When taking the binding to each FcγR by IL6R-B3/IL6R-L resulting from introducing the K439E alteration into IL6R-G1d/IL6R-L containing the sequence of native human IgG1 as 1, the binding of IL6R-G1d/IL6R-L to FcγRIa was 1.3 times; the binding of IL6R-G1d/IL6R-L to FcγRIIaR was 1.1 times; the binding of IL6R-G1d/IL6R-L to FcγRIIaH was 1.1 times, the binding of IL6R-G1d/IL6R-L to FcγRIIb was 1.2 times, and the binding of IL6R-G1d/IL6R-L to FcγRIIIaV was 0.9 times. Thus, for any given FcγR type, the binding of IL6R-B3/IL6R-L to FcγR was comparable to the binding of IL6R-G1d/IL6R-L to FcγR. Thus, the comparison of the binding of each variant to each FcγR with that of IL6R-B3/IL6R-L prior to introduction of the alteration is assumed to be equivalent to the comparison of the binding of each variant to each FcγR with the binding to each FcγR by IL6R-G1d/IL6R-L containing the sequence of native human IgG1. For this reason, in the subsequent Examples below, the binding activity of each variant to each FcγR will be compared to the binding to each FcγR by IL6R-B3/IL6R-L prior to introduction of the alteration. Table 31 shows that all the variants have increased FcγRIIb binding activity as compared to IL6R-B3 prior to introduction of the alteration. The binding activity of IL6R-BF648/IL6R-L, which was the lowest, was increased by 2.6 times, while the binding activity of IL6R-BP230/IL6R-L, which was the highest, was increased by 147.6 times. Regarding the value of KD (IIaR)KD (IIb) that represents the selectivity, the value for IL6R-BP234/IL6R-L, which was the lowest, was 10.0, while the value for IL6R-BP231/IL6R-L, which was the highest, was 32.2. Compared to 0.3 for IL6R-B3/IL6R-L prior to introduction of the alteration, the values imply that all the variants have improved selectivity. All the variants showed lower binding activity to FcγRIa. FcγRIIaH, and FcγRIIIaV than IL6R-B3/IL6R-L prior to introduction of the alteration.

Reference Example 19 X-Ray Crystal Structure Analysis of the Complexes of FcγRIIb Extracellular Region or FcγRIIaR Extracellular Region and Fc Region with Enhanced FcγRIIb Binding

As shown in Reference Example 18, the FcγRIIb binding of variant IL6R-BP230/IL6R-L, whose FcγRIIb binding was enhanced most, was enhanced to about 150 times as compared to IL6R-B3/IL6R-L prior to introduction of the alteration, while the enhancement of its FcγRIIaR binding was suppressed to an extent of about 1.9 times. Thus, IL6R-BP230/IL6R-L is a variant excellent in both FcγRIIb binding and selectivity. However, the present inventors sought a possibility to create more preferable variants with further enhanced FcγRIIb binding while suppressing the FcγRIIaR binding as possible.

As shown in FIG. 39 described in Reference Example 15, in the Fc region with alteration P238D, Asp at position 270 (EU numbering) in its CH2 domain B forms a tight electrostatic interaction with Arg at position 131 in FcγRIIb. This amino acid residue at position 131 is His in FcγRIIIa and FcγRIIaH, while it is Arg in FcγRIIaR like in FcγRIIb. Thus, there is no difference between FcγRIIaR and FcγRIIb in terms of the interaction of the amino acid residue at position 131 with Asp at position 270 (EU numbering) in the CH2 domain B. This is assumed to be a major factor for the poor selectivity between the FcγRIIb binding and FcγRIIaR binding of the Fc region.

On the other hand, the extracellular regions of FcγRIIa and FcγRIIb are 93% identical in amino acid sequence, and thus they share very high homology. Based on the crystal structure analysis of the complex of the Fc region of native IgG1 (hereinafter abbreviated as Fc (WT)) and the extracellular region of FcγRIIaR (J. Imunol. (2011) 187, 3208-3217), a difference found around the interface of their interaction was only three amino acids (Gln127, Leu132, Phe160) between FcγRIIaR and FcγRIIb. Thus, the present inventors predicted that it was extremely difficult to improve the selectivity of the Fc region between the FcγRIIb binding and FcγRIIaR binding.

In this context, the present inventors conceived that, in order to further enhance the FcγRIIb-binding activity of the Fc region and to improve the selectivity of its FcγRIIaR binding, it was important to clarify subtle differences between Fc region-FcγRIIb interaction and Fc region-FcγRIIaR interaction by analyzing not only the three-dimensional structure of the complex of the Fc region with enhanced FcγRIIb binding and the extracellular region of FcγRIIb but also the three-dimensional structure of the complex of the Fc region with enhanced FcγRIIb binding and the extracellular region of FcγRIIaR First, the present inventors analyzed the X-ray crystal structure of the complex of the extracellular region of FcγRIIb or FcγRIIaR and Fc (P208) resulting from eliminating the K439E alteration from the Fc region of IL6R-BP208/IL6R-L created as described in Reference Example 17, which was the variant used as the basis in producing IL6R-BP230/IL6R-L.

(19-1) X-Ray Crystal Structure Analysis of the Complex of Fc (P208) and the Extracellular Region of FcγRIIb [Expression and Purification of Fc (P208)]

Fc (P208) was prepared as described below. First, IL6R-P208 was produced by substituting Lys for Glu at position 439 (EU numbering) in IL6R-BP208, as is in the case of the sequence of native human IgG1. Then, the gene sequence of Fc (P208) spanning from Glu at position 216 (EU numbering) to the C terminus was cloned by PCR using as a template a DNA encoding a variant with a substitution of Ser for Cys at position 220 (EU numbering). Expression vector construction, expression, and purification were achieved according to the method described in Reference Example 1. Meanwhile, Cys at position 220 (EU numbering) in ordinary IgG1 forms a disulfide bond to a Cys in the L chain. When preparing the Fc region alone, the L chain is not coexpressed. Thus, Cys at position 220 was substituted by Ser to avoid unnecessary disulfide bond formation.

[Expression and Purification of the Extracellular Region of FcγRIIb]

The extracellular region of FcγRIIb was prepared according to the method described in Reference Example 2.

[Purification of the Fc (P208)/FcγRIIb Extracellular Region Complex]

0.15 mg of the purified product of Endo F1 (Protein Science (1996) 5, 2617-2622) expressed in E. coli as a fusion protein with glutathione S-transferase was added 1.5 mg of a crystallization sample of the extracellular region of FcγRIIb. This added sample in 0.1 M Bis-Tris buffer (pH 6.5) was allowed to stand at room temperature for three days to cleave off N-type sugar chains except N-acetylglucosamine directly linked to the Asn in the sample of the extracellular region of FcγRIIb. Then, the sample of the extracellular region of FcγRIIb subjected to the sugar chain cleavage treatment was concentrated with a 5000MWCO ultrafiltration filter, and purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 20 mM HEPES (pH7.5)/0.1 M NaCl. Next, Fc (P208) was added in such a way that the extracellular region of FcγRIIb is present in a slightly excessive molar ratio. After concentrating with a 10000MWCO ultrafiltration filter, the purified fraction of the extracellular region of FcγRIIb subjected to the sugar chain cleavage was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7.5)/0.1 M NaCl. The purified fraction prepared as described above was used as a sample of Fc (P208)/FcγRIIb extracellular region complex in the subsequent assessment.

[Crystallization of the Complex of Fc (P208)/FcγRIIb Extracellular Region]

A sample of Fc (P208)/FcγRIIb extracellular region complex concentrated to about 10 mg/ml with a 10000MWCO ultrafiltration filter was crystallized using the hanging drop vapor diffusion method in combination with the seeding method. VDXm plate (Hampton Research) was used for crystallization. Using a reservoir solution of 0.1 M Bis-Tris (pH 6.5)/19% (w/v) PEG3350/0.2 M potassium phosphate dibasic, crystallization drops were prepared at a mixing ratio of reservoir solution:crystallization sample=0.85 μl:0.85 μl. Crystals of the complex obtained under the same condition were crushed with Seed Bead (Hampton Research) to prepare a seed crystal solution. The crystallization drops were added with 0.15 μl of a diluted solution prepared from the seed solution and allowed to stand at 20° C. in sealed reservoir wells. This yielded plate-like crystals.

[X-Ray Diffraction Data Measurements from an Fc (P208)/FcγRIIb Extracellular Region Complex Crystal]

A single crystal of Fc (P208)/FcγRIIb extracellular region complex prepared as described above was soaked into a solution of 0.1 M Bis-Tris (pH 6.5)/24% (w/v) PEG3350/0.2 M potassium phosphate dibasic/20% (v/v) ethylene glycol. Then, the single crystal was fished out of the solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. X-ray diffraction data of the single crystal was collected with Spring-8 BL32XU. During the measurement, the crystal was constantly placed in a nitrogen stream at −178° C. to maintain in a frozen state. A total of 300 X-ray diffraction images of the single crystal were collected using CCD detector MX-225HE (RAYONIX) attached to a beam line with rotating the single crystal 0.6° at a time. Based on the obtained diffraction images, lattice constant determination, diffraction spot indexing, and diffraction data processing were performed using programs Xia2 (J. Appl. Cryst. (2010) 43, 186-190), XDS Package (Acta Cryst. (2010) D66, 125-132) and Scala (Acta Cryst. (2006) D62, 72-82). Finally, diffraction intensity data up to 2.81 Å resolution was obtained. The crystal belongs to the space group C222₁ with lattice constant a=156.69 Å, b=260.17 Å, c=56.85 Å, α=90°, β=900, and γ=90.

[X-Ray Crystal Structure Analysis of Fc (P208)/FcγRIIb Extracellular Region Complex]

The structure of Fc (P208) FcγRIIb extracellular region complex was determined by a molecular replacement method using program Phaser (J. Appl. Cryst. (2007) 40, 658-674). The number of complexes in an asymmetrical unit was estimated to be one from the size of the obtained crystal lattice and the molecular weight of Fc (P208)/FcγRIIb extracellular region complex. The segments spanning the amino acid residues at positions 239-340 of the A chain and at positions 239-340 of the B chain, which were retrieved as an independent coordinate from the structural coordinate of PDB code: 3SGJ for the crystal structure of Fc (WT)/FcγRIIIa extracellular region complex, were used as a model for searching the CH2 domain of the Fc region. Likewise, the segments spanning the amino acid residues at positions 341-444 of the A chain and at positions 341-443 of the B chain, which were retrieved as a coordinate from the structural coordinate of PDB code: 3SGJ, were used as a model for searching the CH3 domain of the Fc region. Finally, the segment spanning the amino acid residues at positions 6-178 of the A chain, which was retrieved from the structural coordinate of PDB code: 2FCB for the crystal structure of the extracellular region of FcγRIIb, was used as a model for searching Fc (P208). The present inventors tried to determine the orientations and positions of the respective search models of the CH3 domain of the Fc region, the extracellular region of FcγRIIb, and the CH2 domain of the Fc region in the crystal lattices based on the rotation function and translation function, but failed to determine the position of one of the CH2 domains. Then, with reference to the crystal structure of the complex of Fc (WT)/FcγRIIIa extracellular region, the position of the last CH2 domain A was determined from an electron density map that was calculated based on the phase determined for the remaining three parts. Thus, the present inventors obtained an initial model for the crystal structure of the complex of Fc (P208)/FcγRIIb extracellular region. The crystallographic reliability factor R value of the structural model for the data of diffracted intensity at 25 to 3.0 Å was 42.6% and Free R value was 43.7% after rigid body refinement where the two CH2 domains and two CH3 domains of the Fc region, and the extracellular region of FcγRIIb were allowed to deviate from the obtained initial structural model. Then, structural model refinement was achieved by repeating structural refinement using program REFMAC5 (Acta Cryst. (2011) D67, 355-367) followed by revision of the structural model performed using program Coot (Acta Cryst. (2010) D66, 486-501) with reference to the electron density maps where the coefficients 2Fo-Fc and Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc calculated according to the structural model, and the phases calculated according to the structural model. Then, further refinement was carried out based on the electron density maps with coefficients of 2Fo-Fc and Fo-Fc by integrating water molecules into the structural model. With 27259 diffracted intensity data at 25 to 2.81 Å resolution, ultimately the crystallographic reliability factor R value was 24.5% and free R value was 28.2% for the structural model comprising 4786 non-hydrogen atoms.

The three-dimensional structure of the complex of Fc (P208)/FcγRIIb extracellular region was determined at a resolution of 2.81 Å by structure analysis. The structure obtained by the analysis is shown in FIG. 44. FcγRIIb extracellular region was revealed to be bound and sandwiched between the two CH2 domains of the Fc region, which resembles the three-dimensional structures of the previously analyzed complexes of Fc (WT), which is the Fc of native IgG, and each of the extracellular regions of FcγRIIIa (Proc. Natl. Acad. Sci. USA (2011) 108, 12669-126674), FcγRIIIb (Nature (2000) 400, 267-273; J. Biol. Chem. (2011) 276, 16469-16477), and FcγRIIa (J. Immunol. (2011) 187 (6), 3208-3217).

A close observation of the complex of Fc (P208)/FcγRIIb extracellular region revealed a change in the loop structure at positions 233 to 239 (EU numbering) following the hinge region in the CH2 domain A of the Fc region due to an influence of the introduced the G237D and P238D alterations as compared to the complex of Fc (WT)/FcγRIIaR extracellular region (FIG. 45). This leads to that the main chain of Asp at position 237 (EU numbering) in Fc (P208) formed a tight hydrogen bond to the side chain of Tyr at position 160 in FcγRIIb (FIG. 46). In both FcγRIIaH and FcγRIIaR, the amino acid residue at position 160 is Phe, which is incapable of forming such a hydrogen bond. This suggests that the above described hydrogen bond has important contribution to the enhancement of the FcγRIIb binding and the acquisition of the FcγRIIa binding selectivity of Fc (P208), i.e., improvement of the FcγRIIb-binding activity and reduction of FcγRIIa-binding activity of Fc (P208).

On the other hand, the side chain of Asp at position 237 (EU numbering) in Fc (P208) forms neither particularly significant interaction in the FcγRIIb binding nor interaction with other residues within the Fc region. Ile at position 332, Glu at position 333, and Lys at position 334 (EU numbering) in the Fc region are located close to Asp at position 237 (EU numbering) (FIG. 47). When the amino acid residues of these positions are substituted by hydrophilic residues to form an interaction with the side chain of Asp at position 237 (EU numbering) in Fc (P208) and the loop structure can be stabilized by the interaction, this can lead to reduction of the entropic energy loss due to the hydrogen bonding between the Fc region and Tyr at position 160 in FcγRIIb and thereby to an increase in the binding free energy, i.e., an increase in the binding activity.

When the X-ray crystal structure of the complex of Fc (P238D) with the P238D alteration and FcγRIIb extracellular region described in Reference Example 15 is compared to the X-ray crystal structure of the complex of Fc (P208) and FcγRIIb extracellular region, deviations are observed at five portions in Fc (P208) as compared to Fc (P238D) and most of the changes are seen only at the side chain level. Meanwhile, a positional deviation at the main chain level due to the Pro-to-Gly alteration at position 271 (EU numbering) is also observed in the CH2 domain B of the Fc region, and in addition there is a structural change in the loop at positions 266 to 270 (EU numbering) (FIG. 48). As described in Reference Example 16, it is suggested that, when Asp at position 270 (EU numbering) in Fc (P238D) forms a tight electrostatic interaction with Arg at position 131 in FcγRIIb, the interaction can induce stereochemical stress at Pro at position 271 (EU numbering). The experiment described herein suggests that the structural change observed with the alteration to Gly for the amino acid at position 271 (EU numbering) is assumed to be a result of elimination of the structural distortion accumulated at Pro prior to the alteration and the elimination results in an increase in the free energy for the FcγRIIb binding, i.e., an increase in the binding activity.

Furthermore, it was demonstrated that, due to the change of the loop structure at positions 266 to 271 (EU numbering), Arg at position 292 (EU numbering) underwent a structural change while being in two states. In this case, the electrostatic interaction (FIG. 48) formed between Arg at position 292 (EU numbering) and Asp at position 268 (EU numbering) which is an altered residue in Fc (P208) can contribute to the stabilization of the loop structure. Since the electrostatic interaction formed between Asp at position 270 (EU numbering) in the loop and Arg at position 131 in FcγRIIb largely contribute to the binding activity of Fc (P208) to FcγRIIb, the stabilization of the loop structure in the binding conformation was likely to reduce the entropic energy loss upon binding. Thus, the alteration is expected to result in an increase in the binding free energy, i.e., an increase in the binding activity.

Moreover, the possibility of alteration to further increase the activity was scrutinized based on the result of structural analysis. Ser at position 239 (EU numbering) was found as a candidate for the site to introduce alteration. As shown in FIG. 49, Ser at position 239 (EU numbering) in the CH2 domain B is present at the position toward which Lys at position 117 in FcγRIIb extends most naturally in structure. However, since the electron density was not observed for Lys at position 117 in FcγRIIb by the analysis described above, the Lys has no definite structure. In this situation, Lys 117 is likely to have only a limited effect on the interaction with Fc (P208). When Ser at position 239 (EU numbering) in the CH2 domain B is substituted with negatively charged Asp or Glu, such an alteration is expected to cause an electrostatic interaction with the positively charged Lys at position 117 in FcγRIIb, thereby resulting in improved FcγRIIb-binding activity.

On the other hand, an observation of the structure of Ser at position 239 (EU numbering) in the CH2 domain A revealed that, by forming a hydrogen bond to the main chain of Gly at position 236 (EU numbering), the side chain of this Ser stabilized the loop structure at positions 233 to 239, including Asp at position 237 (EU numbering) that forms a hydrogen bond to the side chain of Tyr at position 160 in FcγRIIb, following the hinge region (FIG. 46). The stabilization of the loop structure in the binding conformation can reduce the entropic energy loss upon binding, and result in an increase in the binding free energy, i.e., an improvement of the binding activity. Meanwhile, when Ser at position 239 (EU numbering) in the CH2 domain A is substituted with Asp or Glu, the loop structure can become unstable due to loss of the hydrogen bond to the main chain of Gly at position 236 (EU numbering). In addition, the alteration can result in electrostatic repulsion to Asp at position 265 (EU numbering) in close proximity, leading to further destabilization of the loop structure. The energy for the destabilization corresponds to loss of free energy for the FcγRIIb binding, which can result in reduction in the binding activity.

(19-2) X-Ray Crystal Structure Analysis of the Complex of Fc (P208) and FcγRIIaR Extracellular Region [Expression and Purification of the Extracellular Region of FcγRIIaR]

The extracellular region of FcγRIIaR was prepared according to the method described in Reference Example 2.

[Purification of the Complex of Fc (P208)/FcγRIIaR Extracellular Region]

1.5 mg of purified sample of the extracellular region of FcγRIIaR was added with 0.15 mg of the purified product of Endo F1 (Protein Science (1996) 5, 2617-2622) expressed in E. coli as a fusion protein with glutathione S-transferase, 20 μl of 5 U/ml Endo F2 (QA-bio), and 20 μl of 5 U/ml Endo F3 (QA-bio). After 9 days of incubation at room temperature in 0.1 M Na acetate buffer (pH 4.5), the sample was further added with 0.07 mg of the above-described Endo F1, 7.5 μl of the above-described Endo F2, and 7.5 μl of the above-described Endo F3, and was incubated for three days to cleave off N-type sugar chains except N-acetylglucosamine directly linked to the Asn in the sample of the extracellular region of FcγRIIa R. Then, the sample of the extracellular region of FcγRIIaR concentrated with a 10000MWCO ultrafiltration filter and subjected to the above-described sugar chain cleavage treatment was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7)/0. IM NaCl. Next, Fc (P208) was added in such a way that the extracellular region of FcγRIIaR is present in a slightly excessive molar ratio. After concentrating with a 10000MWCO ultrafiltration filter, the purified fraction of the extracellular region of FcγRIIaR subjected to the above-described sugar chain cleavage treatment was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7)/0.1 M NaCl. The purified fraction prepared as described above was used as a sample of Fc (P208)/FcγRIIaR extracellular region complex in the subsequent assessment.

[Crystallization of the Complex of Fc (P208)/FcγRIIaR Extracellular Region]

A sample of Fc (P208)/FcγRIIa R extracellular region complex concentrated to about 10 mg/ml with a 10000MWCO ultrafiltration filter was crystallized using the sitting drop vapor diffusion method. Using a reservoir solution of 0.1 M Bis-Tris (pH 7.5)/26% (w/v) PEG3350/0.2 M ammonium sulfate, crystallization drops were prepared at a mixing ratio of reservoir solution:crystallization sample=0.8 μl:1.0 μl. The drops were tight sealed and allowed to stand at 20° C. This yielded plate-like crystals.

[X-Ray Diffraction Data Measurement from Fc (P208)/FcγRIIaR Extracellular Region Complex Crystal]

A single crystal of Fc (P208)/FcγRIIaR extracellular region complex prepared as described above was soaked into a solution of 0.1 M Bis-Tris (pH 7.5)/27.5% (w/v) PEG3350/0.2 M ammonium sulfate/20% (v/v) glycerol. Then, the crystal was fished out of the solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. X-ray diffraction data of the single crystal was collected from Photon Factory BL-17A of the synchrotron radiation institution in the High Energy Accelerator Research Organization. The crystal was constantly placed in a nitrogen stream at −178° C. to maintain in a frozen state during the measurement. A total of 225 X-ray diffraction images of the single crystal were collected using CCD detector Quantum 315r (ADSC) equipped to the beam line with rotating the single crystal at 0.6° at a time. Based on the obtained diffraction images, lattice constant determination, diffraction spot indexing, and diffraction data processing were performed using programs Xia2 (J. Appl. Cryst. (2010) 43, 186-190), XDS Package (Acta Cyst. (2010) D66, 125-132), and Scala (Acta Cryst. (2006) D62, 72-82). Finally, diffraction intensity data up to 2.87 Å resolution was obtained. The crystal belongs to the space group C222₁ with lattice constant a=154.31 Å, b=257.61 Å, c=56.19 Å, α=90°, β=90°, and γ=90°.

[X-Ray Crystal Structure Analysis of Fc (P208)/FcγRIIaR Extracellular Region Complex]

The structure of Fc (P208)/FcγRIIaR extracellular region complex was determined by a molecular replacement method using program Phaser (J. Appl. Cryst. (2007) 40, 658-674). The number of complexes in an asymmetrical unit was estimated to be one from the size of the obtained crystal lattice and the molecular weight of Fc (P208)/FcγRIIaR extracellular region complex. Using, as a search model, the crystallographic structure of Fc (P208)/FcγRIIb extracellular region complex obtained as described in (19-1), the orientation and position of Fc (P208)/FcγRIIaR extracellular region complex in the crystal lattices were determined based on the rotation function and translation function. The crystallographic reliability factor R value of the structural model for the data of diffracted intensity at 25 to 3.0 Å was 38.4% and Free R value was 30.0% after rigid body refinement where the two CH2 domains and two CH3 domains of the Fc region, and the extracellular region of FcγRIIaR were allowed to independently deviate from the obtained initial structural model. Then, structural model refinement was achieved by repeating structural refinement using program REFMAC5 (Acta Cryst. (2011) D67, 355-367) followed by revision of the structural model performed using program Coot (Acta Cryst. (2010) D66, 486-501) with reference to the electron density maps where the coefficients Fo-Fc and 2Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc calculated according to the model, and the phases calculated according to the model. Finally, further refinement was carried out based on the electron density maps with coefficients Fo-Fc and 2Fo-Fc by integrating water molecules into the structural model. With 24838 diffracted intensity data at 25 to 2.87 Å resolution, ultimately the crystallographic reliability factor R value was 26.3% and free R value was 38.0% for the structural model comprising 4758 non-hydrogen atoms.

The three-dimensional structure of the complex of Fc (P208)/FcγRIIaR extracellular region was determined at a resolution of 2.87 Å by structure analysis. A comparison of the crystal structure between the complex of Fc (P208)/FcγRIIaR extracellular region and the complex of Fc (P208)/FcγRIIb extracellular region described in (19-1) detected almost no difference at the level of overall structure (FIG. 50), reflecting the very high amino acid identity between the two Fcγ receptors.

However, a precise observation of the structures at the electron density level detected some differences that can lead to improvement of the selectivity between the FcγRIIb binding and the FcγRIIaR binding of the Fc region. The amino acid residue at position 160 in FcγRIIaR is not Tyr but Phe. As shown in FIG. 51, the hydrogen bond between the main chain of the amino acid residue at position 237 (EU numbering) in the CH2 domain A of the Fc region and Tyr at position 160 in FcγRIIb, though formed upon binding between FcγRIIb and the Fc region with alteration P238D, is expected not to be formed upon binding between FcγRIIaR and the Fc region with alteration P238D. The absence of the hydrogen bond formation can be a major factor for improving the selectivity between the FcγRIIb binding and the FcγRIIaR binding of the Fc region introduced with alteration P238D. Further comparison at the electron density level showed that, in the Fc region/FcγRIIb complex, electron density was clearly observable for the side chains of Leu at positions 235 and 234 (EU numbering), whereas the electron density of the side chains was unclear in the Fc region/FcγRIIaR complex. This suggests that the loop near position 237 (EU numbering) fluctuates due to the reduced FcγRIIaR interaction around this position. Meanwhile, a structural comparison of the CH2 domain B of the Fc region (FIG. 52) in same region revealed that, in the complex of the Fc region and FcγRIIb, electron density was observable up to Asp at position 237 (EU numbering), whereas, in the complex of the Fc region and FcγRIIaR, electron density was observable up to three residues prior to Asp at position 237 (EU numbering), i.e., up to around Leu at position 234 (EU numbering), suggesting that FcγRIIaR binding forms an interaction over a larger region as compared to the FcγRIIb binding. The finding described above suggests the possibility that, in the CH2 domain A of the Fc region, the region from position 234 to 238 (EU numbering) has a large contribution to the binding between the Fc region and FcγRIIb, while in the CH2 domain B of the Fc region the region from position 234 to 238 (EU numbering) has a large contribution to the binding between the Fc region and FcγRIIaR.

Reference Example 20 Fc Variants for which Alteration Sites were Determined Based on Crystal Structure

As described in Reference Example 19, Asp at position 268 (EU numbering) was suggested to electrostatically interact with Arg at position 292 (EU numbering) (FIG. 48) as a result of the local structural change due to introduction of the alteration P271G in domain B of the variant with enhanced FcγRIIb binding (P208). There is a possibility that the loop structure at positions 266 to 271 (EU numbering) is stabilized by the formation of the interaction, resulting in enhancement of the FcγRIIb binding. Thus, the present inventors assessed whether the FcγRIIb binding of the variant could be enhanced by additional stabilization of its loop structure due to enhancement of the electrostatic interaction by substituting Glu for Asp at position 268 (EU numbering) in the variant. On the other hand, as shown in FIG. 47, Tyr at position 160 in FcγRIIb interacts with the main chain of Asp at position 237 (EU numbering) in domain A of P208. Meanwhile, the side chain of Asp at position 237 (EU numbering) is located close to Ile at position 332, Glu at position 333, and Lys at position 334 (EU numbering) in the molecule without forming any particularly significant interaction. Thus, the present inventors also assessed whether the interaction with Tyr at position 160 in FcγRIIb can be enhanced through stabilization of the loop structure at positions 266 to 271 (EU numbering) due to increased interaction with the side chain of Asp at position 237 (EU numbering) by substituting hydrophilic amino acid residues at the positions described above.

Variants were produced by introducing each of alterations H268E, I332T, I332S, I332E, I332K, E333K, E333R, E333S, E333T, K334S, K334T, and K334E into IL6R-BP230/IL6R-L produced as described in Reference Example 18. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR, Fcγ-RIIb, or FcγRIIIaV) by the method described in Reference Example 2.

The KD value of each variant to each FcγR is shown in Table 32. In the table, “alteration” refers to an alteration introduced into IL6R-BP230. IL6R-B3/IL6R-L which is used as the template to produce IL6R-BP230 is indicated by asterisk (*). KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide in the table shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. Meanwhile, KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγR IIaR by the KD value of each variant for FcγR IIaR. KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb. In Table 32, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

TABLE 32

Both FcγRIIb-binding activity and FcγRIb selectivity of IL6R-BP264/IL6R-L, IL6R-BP465/IL6R-L, IL6R-BP466/IL6R-L, and IL6R-BP470, resulting from introducing alterations H268E, E333K, E333R, and E333T, respectively, into IL6R-BP230/IL6R-L were increased as compared to those of IL6R-BP230/IL6R-L. The FcγRIIb selectivity of IL6R-BP391/IL6R-L introduced with the I332T alteration was reduced while its FcγRIIb-binding activity was increased as compared to IL6R-BP230/IL6R-L.

Reference Example 21 Exhaustive Introduction of Alterations at Amino Acid Residues Around Position 271 (EU Numbering)

In the structural comparison between Fc (P208)/FcγRIIb and Fc (P238D)/FcγRIIb, the most significant difference is found in the structure around position 271 (EU numbering) in the CH2 domain B of the Fc region (FIG. 48). As described in Reference Example 16, it is suggested that, when, in the structure of Fc (P238D)/FcγRIIb, Asp at position 270 (EU numbering) forms a tight electrostatic interaction with Arg at position 131 in FcγRIIb, the interaction can induce stereochemical stress at Pro at position 271 (EU numbering). In the structure of Fc (P208)/FcγRIIb, due to the substitution of Gly for Pro at position 271 (EU numbering), a positional deviation occurred at the main chain level so as to eliminate the structural distortion, resulting in a large structural change around position 271. There is a possibility that additional stabilization of the structure changed around position 271 further reduces the entropic energy loss caused by the binding upon formation of an electrostatic interaction with Arg at position 131 in FcγRIIb. Thus, alterations that enhance the FcγRIIb binding or increase the FcγRIIb selectivity of the Fc region were sought by exhaustive introduction of alterations at amino acid residues around position 271 (EU numbering).

IL6R-BP267 was constructed as a template in exhaustive introduction of alterations by introducing alterations E233D, G237D, P238D, H268E, and P271G into IL6R-B3 (SEQ ID NO: 164). IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa. FcγRIIaH, FcγRIIaR, FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2. The amino acids at positions 264, 265, 266, 267, 269, and 272 (EU numbering) in IL6R-BP267 were substituted with each of 18 types of amino acids, except Cys and the amino acid prior to substitution. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR. FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2. Variants whose FcγRIIb binding has been enhanced or FcγRIIb selectivity has been increased as compared to the FcγRIIb binding or FcγRIIb selectivity of IL6R-BP267/IL6R-L prior to introduction of the alterations are shown in Table 33.

TABLE 33

The KD value of each variant to each FcγR is shown in Table 33. In the table, “alteration” refers to an alteration introduced into IL6R-BP267, which was used as a template. IL6R-B3/IL6R-L which is used as the template to produce IL6R-BP267 is indicated by asterisk (*). In the table, KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. Meanwhile, KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIaR by the KD value of each variant for FcγR IIaR. KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb. In Table 33, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

All the binding activities of variants shown in Table 33 to FcγRIa, FcγRIIaH, and FcγRIIIaV were comparable or reduced as compared to that of IL6R-B3/IL6R-L. Meanwhile, the FcγRIIb-binding activity of variants resulting from adding alterations S267A, V264I, E269D, S267E, V266F, S267G, and V266M, respectively, to IL6R-BP267/IL6R-L were increased as compared to that of IL6R-BP267/IL6R-L prior to addition of alteration. Meanwhile, the KD (IIaR)/KD (IIb) values of variants resulting from adding the S267A, S267G, E272M, E272Q, D265E, E272D, E272N, V266L, E2721, and E272F alterations, respectively, to IL6R-BP267/IL6R-L were increased as compared to that of IL6R-BP267/IL6R-L prior to addition of alteration. This demonstrates that the S267A, S267G, E272M, E272Q, D265E, E272D, E272N, V266L, E2721, and E272F alterations produce the effect to improve the FcγRIIb selectivity.

Reference Example 22 Enhancement of the FcγRIIb Binding by Introduction of Alterations into CH3 Region

A substitution alteration of Leu for Pro at position 396 (EU numbering) has been reported to enhance the FcγRIIb binding (Cancer Res. (2007) 67, 8882-8890). The amino acid at position 396 (EU numbering) is present at a position which is not directly involved in the interaction with FcγR However, the amino acid can be assumed to have an effect on the interaction with FcγR by changing the antibody structure. Thus, the present inventors assessed whether the FcγRIIb binding of the Fc region is enhanced or its FcγRIIb selectivity is increased by exhaustive introduction of amino acid alterations at position 396 (EU numbering) in the Fc region.

IL6R-BP423 was constructed as a template in exhaustive introduction of alterations by introducing alterations E233D, G237D, P238D. S267A, H268E. P271G, and A330R into IL6R-B3 (SEQ ID NO: 164). Variants, in which the amino acid at position 396 (EU numbering) in IL6R-BP423 was substituted with each of 18 types of amino acids, except Cys and the amino acid prior to substitution, were constructed. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR. FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2. The binding of the resulting variants to each FcγR is shown in Table 34.

TABLE 34

In the table, “alteration introduced into IL6R-BP423” refers to an alteration introduced into IL6R-BP423, which was used as a template. IL6R-B3/IL6R-L which is used as the template to produce IL6R-BP423 is indicated by asterisk (*). In the table, KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. Meanwhile, KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγR IIaR by the KD value of each variant for FcγR IIaR. KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb. In Table 34, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

The result shown in Table 34 demonstrates that: the FcγRIIb-binding activity of IL6R-BP456/IL6R-L resulting from introducing alteration P396M into IL6R-BP423/IL6R-L, IL6R-BP455/IL6R-L resulting from introducing alteration P396L into IL6R-BP423/IL6R-L, IL6R-BP464/IL6R-L resulting from introducing alteration P396Y into IL6R-BP423/IL6R-L, IL6R-BP450/IL6R-L resulting from introducing alteration P396F into IL6R-BP423/IL6R-L, IL6R-BP448/IL6R-L resulting from introducing alteration P396D into IL6R-BP423/IL6R-L, IL6R-BP458/IL6R-L resulting from introducing alteration P396Q into IL6R-BP423/IL6R-L, IL6R-BP453/IL6R-L resulting from introducing alteration P3961 into IL6R-BP423/IL6R-L, IL6R-BP449/L6R-L resulting from introducing alteration P396E into IL6R-BP423/IL6R-L. IL6R-BP454/IL6R-L resulting from introducing alteration P396K into IL6R-BP423/IL6R-L, and IL6R-BP459/1L6R-L resulting from introducing alteration P396R into IL6R-BP423/IL6R-L was all increased as compared to that of IL6R-BP423/IL6R-L prior to introduction of the alterations. Meanwhile, the KD (IIaR)/KD (IIb) value of IL6R-BP456/IL6R-L resulting from introducing alteration P396M into IL6R-BP423/IL6R-L was larger as compared to that of IL6R-BP423/IL6R-L prior to introduction of the alteration, demonstrating the improved FcγRIIb selectivity. As seen in Table 34, the binding activity of the prepared variants to FcγRIa, FcγRIIaH, and FcγRIIIaV was all lower than that of IL6R-B3/IL6R-L, which was the parent polypeptide.

Reference Example 23 Preparation of Variants with Enhanced FcγRIIb Binding Using Subclass Sequences

The FcγR binding profile varies depending on the subclass of human IgG. The present inventors assessed whether the difference in the binding activity to each FcγR between IgG1 and IgG4 could be utilized to increase the FcγRIIb-binding activity and/or improve the selectivity. First, IgG1 and IgG4 were analyzed for their binding activity to each FcγR. IL6R-G4d (SEQ ID NO: 165) containing G4d was constructed as the antibody H chain. G4d is an Fc region that lacks the C-terminal Gly and Lys and contains a substitution of Pro for Ser at position 228 (EU numbering) in human IgG4. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the heavy chain of IL6R-G1d or IL6R-G4d were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR. FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2. The binding of the resulting variants to each FcγR is summarized in Table 35.

TABLE 35 KD KD KD KD KD AGAINST AGAINST AGAINST AGAINST AGAINST VARIANT FcγRIa FcγRIIaR FcγRIIaH FcγRIIb FcγRIIIaV NAME (mol/L) (mol/L) (mol/L) (mol/L) (mol/L) IL6R-G1d/ 1.20E−10 9.70E−07 6.50E−07 3.90E−06 4.20E−07 IL6R-L IL6R-G4d/ 6.60E−10 2.10E−06 3.40E−06 2.60E−06 3.40E−06 IL6R-L

It was demonstrated that the FcγRIb binding of IL6R-G4d/IL6R-L was 1.5 times stronger than that of IL6R-G1d/IL6R-L whereas the FcγRIIaR binding of IL6R-G4d/IL6R-L was 2.2 times weaker than that of IL6R-G1d/IL6R-L. Meanwhile, the binding activity of IL6R-G4d/L6R-L to FcγRIa, FcγRIIaH, and FcγRIIIaV was lower than that of IL6R-G1d/L6R-L. The result described above revealed that IL6R-G4d had preferable characteristics as compared to IL6R-G1d in terms of both FcγRIIb-binding activity and selectivity.

FIG. 53 is an alignment to compare the sequences from CH1 to the C terminus (positions 118 to 445 (EU numbering)) of G1d and G4d. In FIG. 53, amino acid residues that are different between G1d and G4d are boxed with thick line. The present inventors assessed whether the FcγRIIb binding could be further increased and/or the FcγRIIb selectivity could be further improved by selecting, from the above-described different amino acids, some portions that are predicted to be involved in the interaction with FcγR, and grafting at least one amino acid residue or more of the G4d sequence, which confers a property preferable from the viewpoint of both FcγRIIb-binding activity and selectivity, to a variant with enhanced FcγRIIb binding.

Specifically, the present inventors produced:

IL6R-BP473 resulting from introducing alteration A327G into IL6R-BP230; IL6R-BP472 resulting from introducing alteration A330S into IL6R-BP230; IL6R-BP471 resulting from introducing alteration P331S into IL6R-BP230; IL6R-BP474 resulting from introducing alterations A330S and P331S into IL6R-BP230; IL6R-BP475 resulting from introducing alterations A327G and A330S into IL6R-BP230; IL6R-BP476 resulting from introducing alterations A327G, A330S, and P331S into IL6R-BP230; and IL6R-BP477 resulting from introducing alterations A327G and P331S into IL6R-BP230. Furthermore, to construct IL6R-BP478, the amino acids from Ala at position 118 to Thr at position 225 (EU numbering) in IL6R-BP230 was substituted with the amino acids from Ala at position 118 to Pro at position 222 (EU numbering) in G4d. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the heavy chain variants described above were purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding activity to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR, Fc-RIIb, or FcγRIIIaV) by the method described in Reference Example 2.

The KD value of each variant to each FcγR is shown in Table 36. KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide in the table shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. In the table, “alteration introduced into IL6R-BP230” refers to an alteration introduced into IL6R-BP230. IL6R-B3/IL6R-L used as the template to produce IL6R-BP230 is indicated by *1. Meanwhile, IL6R-BP478, in which the segment from Ala at position 118 up to Pro at position 222 (EU numbering) in G4d has been substituted for the segment from Ala at position 118 up to Thr at position 225 (EU numbering) in IL6R-BP230, is indicated by *2. KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγR IIaR by the KD value of each variant for FcγR IIaR. KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb. In Table 36, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

TABLE 36

Among the variants shown in Table 36, IL6R-BP473/IL6R-L introduced with alteration A327G had 1.2 times enhanced FcγRIIb binding as compared to that of IL6R-BP230/IL6R-L. Regarding IL6R-BP478/1L6R-L, resulting from substituting the amino acids of Ala at position 118 up to Thr at position 225 (EU numbering) in IL6R-BP230 with the amino acids of Ala at position 118 up to Pro at position 222 (EU numbering) in G4d, its FcγRIIb binding is enhanced by 1.1 times as compared to that of IL6R-BP230/IL6R-L, while FcγRIIaR binding of IL6R-BP478/IL6R-L is reduced by 0.9 times as compared to that of IL6R-BP230/IL6R-L. All the variants also showed lower binding activity to FcγRIa. FcγRIIaH, and FcγRIIIaV as compared to parent polypeptide IL6R-B3/IL6R-L.

Reference Example 24 Assessment of Combinations of Alterations that Enhance the FcγRIIb Binding or Improve the FcγRIIb Selectivity

Additional combinations of the alterations described herein in the sections up to and including “Reference Example 23”, which alterations had been found to be effective in the aspect of enhancement of the FcγRIIb binding or the improvement of the FcγRIIb selectivity, were assessed. Specifically, the alterations that had been assessed to be effective in enhancing the FcγRIIb binding and/or improving the FcγRIIb selectivity were introduced in combination into IL6R-B3 (SEQ ID NO: 164). Furthermore, existing alterations S267E and L328F that enhance the FcγRIIb binding (Seung et al., (Mol. Immunol. (2008) 45, 3926-3933)) were introduced into IL6R-B3 to produce IL6R-BP253 as a comparison control. IL6R-L (SEQ ID NO: 155) was used as the antibody L chain. Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method as described in Reference Example 1. The purified antibodies were assessed for their binding to each FcγR (FcγRIa, FcγRIIaH, FcγRIIaR. FcγRIIb, or FcγRIIIaV) by the method described in Reference Example 2.

The KD value of each variant to each FcγR is shown in Table 37. In the table, “alteration” refers to an alteration introduced into IL6R-B3 (SEQ ID NO: 164). IL6R-B3/IL6R-L which is used as the template to produce each variant is indicated by asterisk (*). KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγRIIb by the KD value of each variant for FcγRIIb. Meanwhile, KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for FcγR IIaR by the KD value of each variant for FcγRIIaR. KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaR by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb as compared to FcγRIIaR. Meanwhile, KD (IIaH)/KD (IIb) shows the value obtained by dividing the KD value of each variant for FcγRIIaH by the KD value of the variant for FcγRIIb. The greater the value, the higher the selectivity to FcγRIIb as compared to FcγRIIaH. In Table 37, the numeral in the gray-filled cells indicates that the binding of FcγR to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:

KD=C·R _(max)/(R _(eq)−RI)−C  [Equation 2]

described in Reference Example 2.

TABLE 37

Among the variants shown in Table 37, IL6R-BP253/IL6R-L added with the existing alterations that enhance the FcγRIIb binding exhibited FcγRIIb- and FcγRIIaR-binding activities increased to 277 times and 529 times those of IL6R-B3/IL6R-L prior to introduction of the alterations, respectively. Furthermore, the FcγRIa-binding activity of IL6R-BP253/IL6R-L was also greater than that of IL6R-B3/IL6R-L. Meanwhile, the FcγRIIaH binding and FcγRIIIaV binding of IL6R-BP253/IL6R-L were reduced as compared to those of IL6R-B3/IL6R-L. Among other variants, IL6R-BP436/IL6R-L and IL6R-BP438/IL6R-L showed an FcγRIa binding slightly enhanced as compared to that of IL6R-B3/IL6R-L prior to introduction of the alterations. All other variants showed a reduced FcγRIa binding. In addition, all the variants exhibited reduced FcγRIIaH binding and FcγRIIIaV binding as compared to those of IL6R-B3/IL6R-L.

Regarding IL6R-BP489/IL6R-L, IL6R-BP487/IL6R-L, IL6R-BP499/IL6R-L. IL6R-BP498/IL6R-L, IL6R-BP503/IL6R-L, IL6R-BP488/IL6R-L, IL6R-BP490/IL6R-L, IL6R-BP445/IL6R-L, IL6R-BP507/IL6R-L, IL6R-491/IL6R-L. IL6R-BP506/IL6R-L, IL6R-BP511/IL6R-L, IL6R-BP502/IL6R-L, IL6R-BP510/IL6R-L, IL6R-BP497/IL6R-L, IL6R-BP436/IL6R-L, IL6R-BP423/IL6R-L, IL6R-BP440/IL6R-L, IL6R-BP429/IL6R-L, IL6R-BP438/IL6R-L. IL6R-BP426/IL6R-L, IL6R-BP437/IL6R-L, IL6R-BP439/IL6R-L, IL6R-BP494/IL6R-L, IL6R-BP425/IL6R-L, and IL6R-BP495/IL6R-L, their FcγRIIb binding was stronger than that of IL6R-BP253/IL6R-L added with the existing alterations that enhance the FcγRIIb binding. Among these, when taking the binding of IL6R-B3/IL6R-L as 1, the enhancement level ranges from 321 times to 3100 times, corresponding to from IL6R-BP495/IL6R-L which showed the weakest FcγRIIb binding to IL6R-BP489/IL6R-L which showed the strongest binding.

The KD (IIaR)/KD (IIb) value of IL6R-BP479/IL6R-L, which was the lowest, was 16.1, while the value of IL6R-BP493/1L6R-L, which was the highest, was 52.1. Thus, the values of the two variants are higher than 0.2 of IL6R-BP253/IL6R-L. Meanwhile, the KD (IIaH)/KD (IIb) value of IL6R-BP480/IL6R-L, which was the lowest, was 107.7, while the value of IL6R-BP426/IL6R-L, which was the highest, was 8362. Thus, the values of the two variants are higher than 107.1 of IL6R-BP253/IL6R-L. The results described above demonstrate that the FcγRIIb-binding activity of all the variants shown in Table 37 has been increased as compared to the variants added with the existing alterations that enhance the FcγRIIb binding. Furthermore, regardless of whether the FcγR IIa is FcγR IIaR or FcγR IIaH, the FcγRIIb selectivity of the variants shown in Table 37 has been improved relative to the variants added with the existing alterations.

Reference Example 25 Acquisition of Antibodies that Bind to IL-6 Receptor in Ca-Dependent Manner from a Human Antibody Library Using Phage Display Technology (25-1) Preparation of a Phage Display Library for Naive Human Antibodies

A phage display library for human antibodies, consisting of multiple phages presenting the Fab domains of mutually different human antibody sequences, was constructed according to a method known to those skilled in the art using a poly A RNA prepared from human PBMC, and commercial human poly A RNA as a template.

(25-2) Acquisition of Antibody Fragments that Bind to Antigen in Ca-Dependent Manner from the Library by Bead Panning

The constructed phage display library for naive human antibodies was subjected to initial selection through concentration of only antibody fragments having an antigen (IL-6 receptor)-binding ability or concentration of antibody fragments using a Ca concentration-dependent antigen (IL-6 receptor)-binding ability as an indicator. Concentration of antibody fragments using a Ca concentration-dependent antigen (IL-6 receptor)-binding ability as an indicator were conducted through elution of the phage library phages bound to IL-6 receptor in the presence of Ca ions with EDTA that chelates the Ca ions Biotinylated IL-6 receptor was used as an antigen.

Phages were produced from Escherichia coli carrying the constructed phage display phagemid. A phage library solution was obtained by diluting with TBS a phage population precipitated by adding 2.5 M NaCl/10% PEG to the E. coli culture solution in which the phages were produced. Subsequently, BSA and CaCl₂ were added to the phage library solution at a final concentration of 4% BSA and 1.2 mM of calcium ion concentration. A common panning method using an antigen immobilized on magnetic beads was referred to as a panning method (J. Immunol. Methods. (2008) 332 (1-2), 2-9; J. Immunol. Methods. (2001) 247 (1-2), 191-203; Biotechnol. Prog. (2002) 18(2) 212-20; Mol. Cell Proteomics (2003) 2 (2), 61-9). NeutrAvidin coated beads (Sera-Mag SpeedBeads NeutrAvidin-coated) or Streptavidin coated beads (Dynabeads M-280 Streptavidin) were used as magnetic beads.

Specifically, 250 μmol of the biotin-labeled antigen was added to the prepared phage library solution to allow the contact of said phage library solution with the antigen at room temperature for 60 minutes. Magnetic beads, blocked with BSA, were added to be bound to antigen-phage complexes at room temperature for 15 minutes. The beads were washed once with 1 mL of 1.2 mM CaCl₂/TBS (TBS containing 1.2 mM CaCl₂). Subsequently, a phage solution was recovered by a general elution method to concentrate an antibody fragment having an IL-6 receptor-binding ability, or by elution from beads suspended in 2 mM EDTA/TBS (TBS containing 2 mM EDTA) to concentrate an antibody fragment using an IL-6 receptor-binding ability in a Ca concentration-dependent manner as an indicator. The recovered phage solution was added to 10 mL of the E. coli strain TG1 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was cultured with gentle stirring at 37° C. for 1 hour to allow the phages to infect the E. coli. The infected E. coli was inoculated into a 225 mm×225 mm plate. Subsequently, the phages were recovered from the culture medium of the E. coli after inoculation to prepare a phage library solution.

In the second and subsequent panning, the phages were enriched using the Ca-dependent binding ability as an indicator. Specifically, 40 pmol of the biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library with the antigen at room temperature for 60 minutes. Magnetic beads, blocked with BSA, were added to be bound to antigen-phage complexes at room temperature for 15 minutes. The beads were washed with 1 mL of 1.2 mM CaCl₂/TBST and 1.2 mM CaCl₂/TBS. Subsequently, the beads, to which 0.1 mL of 2 mM EDTA/TBS was added, were suspended at room temperature. Immediately after that, the beads were separated using a magnetic stand to collect a phage solution. The recovered phage solution was added to 10 mL of the E. coli strain TG1 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was cultured with gentle stirring at 37° C. for 1 hour to allow the phages to infect the E. coli. The infected E. coli was inoculated into a 225 mm×225 mm plate. Subsequently, the phages were recovered from the culture medium of the E. coli after inoculation to collect a phage library solution. The panning using the Ca-dependent binding ability as an indicator was repeated several times.

(25-3) Examination by Phage ELISA

A phage-containing culture supernatant was collected according to a routine method (Methods Mol. Biol. (2002) 178, 133-145) from a single colony of E. coli, obtained as described above.

A culture supernatant containing phages, to which BSA and CaCl₂ were added at a final concentration of 4% BSA and 1.2 mM of calcium ion concentration was subjected to ELISA as described below. A StreptaWell 96 microtiter plate (Roche) was coated overnight with 100 μL of PBS containing the biotin-labeled antigen. Each well of said plate was washed with PBST to remove the antigen, and then the wells were blocked with 250 μL of 4% BSA-TBS for 1 hour or longer. Said plate with the prepared culture supernatant added to each well, from which the 4% BSA-TBS was removed, was allowed to stand undisturbed at 37° C. for 1 hour, allowing the binding of phage-presenting antibody to the antigen present in each well. To each well washed with 1.2 mM CaCl₂/TBST, 1.2 mM CaCl₂/TBS or 1 mM EDTA/TBS was added. The plate was allowed to stand undisturbed for 30 minutes at 37° C. for incubation. After washing with 1.2 mM CaCl₂/TBST, an HRP-conjugated anti-M13 antibody (Amersham Pharmacia Biotech) diluted with TBS at a final concentration of 4% BSA and 1.2 mM of ionized calcium concentration was added to each well, and the plate was incubated for 1 hour. After washing with 1.2 mM CaCl₂/TBST, the chromogenic reaction of the solution in each well with a TMB single solution (ZYMED) added was stopped by adding sulfuric acid. Subsequently, said developed color was measured by measuring absorbance at 450 nm.

As a result of the above phage ELISA, the base sequence of a gene amplified with specific primers and an antibody fragment identified as having a Ca-dependent antigen-binding ability as a template was analyzed.

(25-4) Antibody Expression and Purification

As a result of the above phage ELISA, a clone identified as having a Ca-dependent antigen-binding ability was introduced into an expression plasmid for animal cells. Antibodies were expressed as described below. FreeStyle 293-F strain (Invitrogen) derived from human fetal kidney cells was suspended in FreeStyle 293 Expression Medium (Invitrogen), followed by inoculation of 3 mL into each well of a 6-well plate at a cell density of 1.33×10⁶ cells/mL. The prepared plasmid was introduced into the cells by lipofection. The cells were cultured for 4 days in a CO₂ incubator (37° C., 8% CO₂, 90 rpm). Antibodies were purified from the culture supernatant obtained above by a method known in the art using rProtein A Sepharose™ Fast Flow (Amersham Biosciences). Absorbance of the purified antibody solution was measured at 280 nm using a spectrophotometer. Antibody concentration was calculated from the measurements obtained using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4, 2411-2423).

Reference Example 26 Examination of Ca-Dependent Binding Ability of the Obtained Antibodies to Human IL-6 Receptor

To examine whether or not the binding activities of antibodies 6RL#9-IgG1 [heavy chain SEQ ID NO: 117; light chain SEQ ID NO: 118] and FH4-IgG1 [heavy chain SEQ ID NO: 115; light chain SEQ ID NO: 116], obtained in Reference Example 25, to human IL-6 receptor are Ca-dependent, the kinetic analysis of the antigen-antibody reactions of these antibodies with human IL-6 receptor was conducted using Biacore T100 (GE Healthcare). H54/L28-IgG1 [heavy chain SEQ ID NO: 113; light chain SEQ ID NO: 114], described in WO 2009/125825, was used as a control antibody that has no Ca-dependent binding activity to human IL-6 receptor. The kinetic analysis of the antigen-antibody reactions was conducted in solutions with 2 mM and 3 μM calcium ion concentrations, set as high and low calcium ion concentration conditions, respectively. The antibody of interest was captured on Sensor chip CM4 (GE Healthcare) on which an appropriate amount of Protein A (Invitrogen) was immobilized by an amine coupling method. Two buffers [10 mM ACES, 150 mM NaCl, 0.05% (w/v) Tween 20, and 2 mM CaCl₂ (pH 7.4) or 10 mM ACES, 150 mM NaCl, 0.05% (w/v) Tween 20, and 3 μmol/L CaCl₂ (pH 7.4)] were used as running buffers. These buffers were used for diluting human IL-6 receptor. All the measurements were conducted at 37° C.

In the kinetic analysis of antigen-antibody reaction using H54L28-IgG1 antibody, the H54L28-IgG1 antibody captured on the sensor chip was allowed to interact with IL-6 receptor by injecting a diluent of IL-6 receptor and running buffer (blank) at a flow rate of 20 μL/min for 3 minutes. Subsequently, after the dissociation of IL-6 receptor was observed using running buffer at a flow rate of 20 L/min for 10 minutes, the sensor chip was regenerated by injecting 10 mM glycine-HCl (pH 1.5) at a flow rate 30 μL/min for 30 seconds. Kinetics parameters, binding rate constant (ka) (1/Ms) and dissociation rate constant (kd) (1/s), were calculated from the sensorgrams obtained in the measurement. These values were used to calculate the dissociation constant (KD) (M) of the H54L28-IgG1 antibody for human IL-6 receptor. Each parameter was calculated using the Biacore T100 Evaluation Software (GE Healthcare).

In the kinetic analysis of antigen-antibody reaction using FH4-IgG1 and 6RL#9-IgG1 antibodies, the FH4-IgG1 or 6RL#9-IgG1 antibody captured on the sensor chip was allowed to interact with IL-6 receptor by injecting a diluent of IL-6 receptor and running buffer (blank) at a flow rate of 5 μL/min for 15 minutes. Subsequently, the sensor chip was regenerated by injecting 10 mM glycine-HCl (pH 1.5) at a flow rate 30 μL/min for 30 seconds. Dissociation constants (KD) (M) were calculated from the sensorgrams obtained in the measurement, using a steady-state affinity model. Each parameter was calculated using the Biacore T100 Evaluation Software (GE Healthcare).

The dissociation constants (KD) between each antibody and IL-6 receptor in the presence of 2 mM CaCl₂, determined by the above method, are shown in Table 38.

TABLE 38 ANTIBODY H54/L28-IgG1 FH4-IgG1 6RL#9-IgG1 kD (M) 1.9E−9 5.9E−7 2.6E−7

The KD value of the H54/L28-IgG1 antibody under the condition of 3 μM Ca concentration can be calculated in the same manner as in the presence of 2 mM Ca concentration. Under the condition of 3 μM Ca concentration, FH4-IgG1 and 6RL#9-IgG1 antibodies were barely observed to be bound to IL-6 receptor, thus the calculation of KD values by the method described above is difficult. However, the KD values of these antibodies under the condition of 3 μM Ca concentration can be estimated using Equation 1 (Biacore T100 Software Handbook, BR-1006-48, AE 01/2007) described below.

R _(eq) =C×Rmax/(KD+C)+RI  [Equation 1]

The meaning of each parameter in the aforementioned [Equation 1] is as follows:

Req (RU): Steady state binding levels Rmax (RU): Analyte binding capacity of the surface RI (RU): Bulk refractive index contribution in the sample C (M): Analyte concentration KD (M): Equilibrium dissociation constant

The approximate results of dissociation constant KD values for the antibodies and IL-6 receptor at a Ca concentration of 3 μM, estimated using the above-described [Equation 1], are shown in Table 39. In Table 39, the Req, Rmax, RI, and C values are estimated based on the assay result.

TABLE 39 ANTIBODY H54/L28-IgG1 FH4-IgG1 6RL#9-IgG1 Req(RU) 5 10 Rmax(RU) 39 72 RI(RU) 0 0 C(M)   5E−06   5E−06 KD(M) 2.2E−9 3.4E−05 3.1E−05

Based on the findings described above, it was predicted that the KD between IL-6 receptor and FH4-IgG1 antibody or 6RL#9-IgG1 antibody was increased by about 60 or 120 times (the affinity was reduced by 60 or 120 times or more) when the concentration of CaCl₂ in the buffer was decreased from 2 mM to 3 μM.

Table 40 summarizes the KD values to IL-6 receptor at CaCl₂ concentrations of 2 mM and 3 μM and the Ca dependency for the three types of antibodies H54/L28-IgG1, FH4-IgG1, and 6RL#9-IgG1.

TABLE 40 H54/L28- ANTIBODY IgG1 FH4-IgG1 6RL#9-IgG1 KD (M) (2 mM CaCl₂) 1.9E−9 5.9E−7 2.6E−7 KD (M) (3 μM CaCl₂) 2.2E−9 3.4E−5 OR MORE 3.1E−5 OR MORE Ca DEPENDENCY ABOUT ABOUT 60 TIMES ABOUT THE SAME OR MORE 120 TIMES OR MORE

No difference in the binding of the H54/L28-IgG1 antibody to IL-6 receptor due to the difference in Ca concentration was observed. On the other hand, the binding of FH4-IgG1 and 6RL#9-IgG1 antibodies to IL-6 receptor was observed to be significantly attenuated under the condition of the low Ca concentration (Table 40).

Reference Example 27 Examination of Calcium Ion Binding to the Antibody Obtained

Subsequently, the intermediate temperature of thermal denaturation (Tm value) was measured by differential scanning calorimetry (DSC) as an indicator for examining calcium ion binding to the antibody (MicroCal VP-Capillary DSC, MicroCal). The intermediate temperature of thermal denaturation (Tm value) is an indicator of stability. The intermediate temperature of thermal denaturation (Tm value) becomes higher when a protein is stabilized through calcium ion binding, as compared with no calcium ion binding (J. Biol. Chem. (2008) 283, 37, 25140-25149). The binding activity of calcium ion to antibody was examined by examining changes in the Tm value of the antibody depending on the changes in the calcium ion concentration of the antibody solution. The purified antibody was subjected to dialysis (EasySEP, TOMY) using an external solution of 20 mM Tris-HCl, 150 mM NaCl, and 2 mM CaCl₂ (pH 7.4), or 20 mM Tris-HCl, 150 mM NaCl, and 3 μM CaCl₂ (pH 7.4). DSC measurement was conducted at a heating rate of 240° C./hr from 20 to 115° C. using an antibody solution prepared at about 0.1 mg/mL with the dialysate as a test substance. The intermediate temperatures of thermal denaturation (Tm values) of the Fab domains of each antibody, calculated based on the denaturation curve obtained by DSC, are shown in Table 41.

TABLE 41 CALCIUM ION CONCENTRATION ΔTm (° C.) ANTIBODY 3 μM 2 mM 2 mM − 3 μM H54/L28-IgG1 92.87 92.87 0.00 FH4-IgG1 74.71 78.97 4.26 6RL#9-IgG1 77.77 78.98 1.21

From the results shown in Table 41, it is indicated that the Tm values of the Fab of the FH4-IgG1 and 6RL#9-IgG1 antibodies, which show a calcium-dependent binding ability, varied with changes in the calcium ion concentration, while the Tm value of the Fab of the H54/L28-IgG1 antibody which shows no calcium-dependent binding ability did not vary with changes in the calcium ion concentration. The variation in the Tm values of the Fab of the FH4-IgG1 and 6RL#9-IgG1 antibodies demonstrates that calcium ions bound to these antibodies to stabilize the Fab portions. The above results show that calcium ions bound to the FH4-IgG1 and 6RL#9-IgG1 antibodies, while no calcium ion bound to the H54/L28-IgG1 antibody.

Reference Example 28 Identification of Calcium Ion-Binding Site in Antibody 6RL#9 by X-Ray Crystal Structure Analysis (28-1) X-Ray Crystal Structure Analysis

As described in Reference Example 27, the measurements of thermal denaturation temperature Tm suggested that antibody 6RL#9 binds to calcium ion. However, it was unpredictable which portion of antibody 6RL#9 binds to calcium ion. Then, by using the technique of X-ray crystal structure analysis, residues of antibody 6RL#9 that interact with calcium ion were identified.

(28-2) Expression and Purification of Antibody 6RL#9

Antibody 6RL#9 was expressed and purified for X-ray crystal structure analysis. Specifically, animal expression plasmids constructed to be capable of expressing the heavy chain (SEQ ID NO: 117) and light chain (SEQ ID NO: 118) of antibody 6RL#9 were introduced transiently into animal cells. The constructed plasmids were introduced by the lipofection method into cells of human fetal kidney cell-derived FreeStyle 293-F (Invitrogen) suspended in 800 ml of the FreeStyle 293 Expression Medium (Invitrogen) (final cell density: 1×10⁶ cells/mL). The plasmid-introduced cells were cultured in a CO₂ incubator (37° C., 8% CO₂, 90 rpm) for five days. From the culture supernatant obtained as described above, antibodies were purified by a method known to those skilled in the art using the rProtein A Sepharose™ Fast Flow (Amersham Biosciences). Absorbance at 280 nm of purified antibody solutions was measured using a spectrophotometer. Antibody concentrations were calculated from the measured values using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4, 2411-2423).

(28-3) Purification of Antibody 6RL#9 Fab Fragment

Antibody 6RL#9 was concentrated to 21 mg/ml using an ultrafilter with a molecular weight cutoff of 10,000 MWCO. A 5 mg/mL antibody sample (2.5 mL) was prepared by diluting the antibody solution using 4 mM L-cysteine/5 mM EDTA/20 mM sodium phosphate buffer (pH 6.5). 0.125 mg of papain (Roche Applied Science) was added to the sample. After stirring, the sample was incubated at 35° C. for two hours. After incubation, a tablet of Protease Inhibitor Cocktail Mini, EDTA-free (Roche Applied Science) was dissolved in 10 ml of 25 mM MES buffer (pH 6) and added to the sample. The sample was incubated on ice to stop the papain proteolytic reaction. Then, the sample was loaded onto a 1-ml cation-exchange column HiTrap SP HP (GE Healthcare) equilibrated with 25 mM MES buffer (pH 6), downstream of which a 1-ml HiTrap MabSelect Sure Protein A column (GE Healthcare) was connected in tandem. A purified fraction of the Fab fragment of antibody 6RL#9 was obtained by performing elution with a linear NaCl concentration gradient up to 300 mM in the above-described buffer. Then, the resulting purified fraction was concentrated to about 0.8 ml using a 5000 MWCO ultrafilter. The concentrate was loaded onto a gel filtration column Superdex 200 10/300 GL (GE Healthcare) equilibrated with 100 mM HEPES buffer (pH 8) containing 50 mM NaCl. The purified Fab fragment of antibody 6RL#9 for crystallization was eluted from the column using the same buffer. All the column treatments described above were carried out at a low temperature of 6 to 7.5° C.

(28-4) Crystallization of the Antibody 6RL#9 Fab Fragment in the Presence of Ca

Seed crystals of the 6RL#9 Fab fragment were prepared in advance under general conditions. Then, the purified Fab fragment of antibody 6RL#9 in 5 mM CaCl₂ was concentrated to 12 mg/ml with a 5000 MWCO ultrafilter. Next, the sample concentrated as described above was crystallized by the hanging drop vapor diffusion method using 100 mM HEPES buffer (pH 7.5) containing 20% to 29% PEG4000 as a reservoir solution. The above-described seed crystals were crushed in 100 mM HEPES buffer (pH 7.5) containing 29% PEG4000 and 5 mM CaCl₂, and serially diluted to 100 to 10,000 folds. Then, 0.2 μL of diluted solutions were combined with a mixture of 0.8 μL of the reservoir solution and 0.8 μL of the concentrated sample to prepare crystallization drops on a glass cover slide. The crystallization drops were allowed to stand at 20° C. for two to three days to prepare thin plate-like crystals. X-ray diffraction data were collected using the crystals.

(28-5) Crystallization of the Antibody 6RL#9 Fab Fragment in the Absence of Ca

The purified Fab fragment of antibody 6RL#9 was concentrated to 15 mg/ml using a 5000 MWCO ultrafilter. Then, the sample concentrated as described above was crystallized by the hanging drop vapor diffusion method using 100 mM HEPES buffer (pH 7.5) containing 18% to 25% PEG4000 as a reservoir solution. Crystals of the antibody 6RL#9 Fab fragment obtained in the presence of Ca were crushed in 100 mM HEPES buffer (pH 7.5) containing 25% PEG4000, and serially diluted to 100 to 10,000 folds. Then, 0.2 μL of diluted solutions were combined with a mixture of 0.8 μL of the reservoir solution and 0.8 μL of the concentrated sample to prepare crystallization drops on a glass cover slide. The crystallization drops were allowed to stand at 20° C. for two to three days to prepare thin plate-like crystals. X-ray diffraction data were collected using the crystals.

(28-6) X-Ray Diffraction Data Measurement of Fab Fragment Crystal from Antibody 6RL#9 in the Presence of Ca

Crystals of the Fab fragment of antibody 6RL#9 prepared in the presence of Ca were soaked into 100 mM HEPES buffer (pH 7.5) solution containing 35% PEG4000 and 5 mM CaCl₂. The single crystal was fished out of the exterior solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. X-ray diffraction data of the frozen crystal was collected from beam line BL-17A of the Photon Factory in the High Energy Accelerator Research Organization. The frozen crystal was constantly placed in a nitrogen stream at −178° C. to maintain in a frozen state during the measurement. A total of 180 diffraction images were collected using the CCD detector Quantum315r (ADSC) attached to the beam line with rotating the crystal 1° at a time. Lattice constant determination, diffraction spot indexing, and diffraction data analysis were performed using programs Xia2 (CCP4 Software Suite), XDS Package (Walfgang Kabsch), and Scala (CCP4 Software Suite). Finally, diffraction intensity data up to 2.2 Å resolution was obtained. The crystal belongs to the space group P2₁2₁2₁ with lattice constant a=45.47 Å, b=79.86 Å, c=116.25 Å, α=90°, β=90°, and γ=90°.

(28-7) X-Ray Diffraction Data Measurement of the Fab Fragment Crystal from Antibody 6RL#9 in the Absence of Ca

Crystals of the Fab fragment of antibody 6RL#9 prepared in the absence of Ca were soaked in 100 mM HEPES buffer (pH 7.5) solution containing 35% PEG4000. The single crystal was fished out of the exterior solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. X-ray diffraction data of the frozen crystal was collected from beam line BL-5A of the Photon Factory in the High Energy Accelerator Research Organization. The frozen crystal was constantly placed in a nitrogen stream at −178° C. to maintain in a frozen state during the measurement. A total of 180 diffraction images were collected using the CCD detector Quantum210r (ADSC) attached to the beam line with rotating the crystal 1° at a time. Lattice constant determination, diffraction spot indexing, and diffraction data analysis were performed using programs Xia2 (CCP4 Software Suite), XDS Package (Walfgang Kabsch), and Scala (CCP4 Software Suite). Finally, diffraction intensity data up to 2.3 Å resolution was obtained. The crystal belongs to the space group P2₁2₁2₁ with lattice constant a=45.40 Å, b=79.63 Å, c=116.07 Å, α=90°, β=90°, γ=900, and thus is structurally identical to the crystal prepared in the presence of Ca.

(28-8) Structural Analysis of the Fab Fragment Crystal from Antibody 6RL#9 in the Presence of Ca

The crystal structure of the antibody 6RL#9 Fab fragment in the presence of Ca was determined by a molecular replacement method using the Phaser program (CCP4 Software Suite). The number of molecules in an asymmetrical unit was estimated to be one from the size of crystal lattice and molecular weight of the antibody 6RL#9 Fab fragment. Based on the primary sequence homology, a portion of amino acid positions 112 to 220 from A chain and a portion of amino acid positions 116 to 218 from B chain in the conformational coordinate of PDB code 1ZA6 were used as model molecules for analyzing the CL and CH1 regions. Then, a portion of amino acid positions 1 to 115 from B chain in the conformational coordinate of PDB code 1ZA6 was used as a model molecule for analyzing the VH region. Finally, a portion of amino acid positions 3 to 147 of the light chain in the conformational coordinate of PDB code 2A9M was used as a model molecule for analyzing the VL region. Based on this order, an initial structure model for the antibody 6RL#9 Fab fragment was obtained by determining from translation and rotation functions the positions and orientations of the model molecules for analysis in the crystal lattice. The crystallographic reliability factor R for the reflection data at 25 to 3.0 Å resolution was 46.9% and Free R was 48.6% after rigid body refinement where the VH, VL, CH1, and CL domains were each allowed to deviate from the initial structure model. Then, model refinement was achieved by repeating structural refinement using program Refmac5 (CCP4 Software Suite) followed by model revision performed using program Coot (Paul Emsley) with reference to the Fo-Fc and 2Fo-Fc electron density maps where the coefficients Fo-Fc and 2Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc calculated based on the model, and the phases. The final refinement was carried out using program Refmac5 (CCP4 Software Suite) based on the Fo-Fc and 2Fo-Fc electron density maps by adding water molecule and Ca ion into the model. With 21,020 reflection data at 25 to 2.2 Å resolution, eventually the crystallographic reliability factor R became 20.0% and free R became 27.9% for the model consisting of 3440 atoms.

(28-9) Structural Analysis of the Fab Fragment Crystal from Antibody 6RL#9 in the Absence of Ca

The crystal structure of the antibody 6RL#9 Fab fragment in the absence of Ca was determined based on the structure of the crystal prepared in the presence of Ca. Water and Ca ion molecules were omitted from the conformational coordinate of the crystal of the antibody 6RL#9 Fab fragment prepared in the presence of Ca. The crystallographic reliability factor R for the data of reflection at 25 to 3.0 Å resolution was 30.3% and Free R was 31.7% after the rigid body refinement where the VH, VL, CH1, and CL domains were each allowed to deviate. Then, model refinement was achieved by repeating structural refinement using program Refmac5 (CCP4 Software Suite) followed by model revision performed using program Coot (Paul Emsley) with reference to the Fo-Fc and 2Fo-Fc electron density maps where the coefficients Fo-Fc and 2Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc calculated based on the model, and the phases. The final refinement was carried out using program Refmac5 (CCP4 Software Suite) based on the Fo-Fc and 2Fo-Fc electron density maps by adding water molecule into the model. With 18,357 reflection data at 25 to 2.3 Å resolution, eventually the crystallographic reliability factor R became 20.9% and free R became 27.7% for the model consisting of 3351 atoms.

(28-10) Comparison of X-Ray Crystallographic Diffraction Data of the Fab Fragments of Antibody 6RL#9 Between in the Presence and Absence of Ca

When the crystal structures of the Fab fragments of antibody 6RL#9 are compared between in the presence and absence of Ca, significant changes are seen in the heavy chain CDR3. The structure of the heavy chain CDR3 of the antibody 6RL#9 Fab fragment determined by X-ray crystal structure analysis is shown in FIG. 54. Specifically, a calcium ion resided at the center of the heavy chain CDR3 loop region of the antibody 6RL#9 Fab fragment crystal prepared in the presence of Ca. The calcium ion was assumed to interact with positions 95, 96, and 100a (Kabat numbering) of the heavy chain CDR3. It was believed that the heavy chain CDR3 loop which is important for the antigen binding was stabilized by calcium binding in the presence of Ca, and became an optimum structure for antigen binding. There is no report demonstrating that calcium binds to the antibody heavy chain CDR3. Thus, the calcium-bound structure of the antibody heavy chain CDR3 is a novel structure.

The calcium-binding motif present in the heavy chain CDR3, revealed in the structure of the Fab fragment of the 6RL#9 antibody may also become a new design element for the Ca library for obtaining antigen-binding domain included in the antigen-binding molecule of the present invention whose antigen-binding activity varies depending on the calcium ion concentration. The calcium-binding motif was introduced into a light chain variable region in later-described Reference Examples 38 and 39, and for example, a library containing the heavy chain CDR3 of the 6RL#9 antibody and flexible residues in other CDRs including the light chain is thought to be possible.

Reference Example 29 Preparation of Antibodies that Bind to IL-6 in a Ca-Dependent Manner from a Human Antibody Library Using Phage Display Techniques (29-1) Construction of a Phage Display Library of Naive Human Antibodies

A human antibody phage display library containing multiple phages that display various human antibody Fab domain sequences was constructed by a method known to those skilled in the art using, as a template, polyA RNA prepared from human PBMC, commercially available human polyA RNA, and such.

(29-2) Preparation of Antibody Fragments that Bind to the Antigen in a Ca-Dependent Manner from Library by Bead Panning

Primary selection from the constructed phage display library of naive human antibodies was carried out by enriching antibody fragments that have antigen (IL-6)-binding activity. The antigen used was biotin-labeled IL-6.

Phages were produced from E. coli carrying the constructed phagemid for phage display. To precipitate the phages produced by E. coli, 2.5 M NaCl/10% PEG was added to the E. coli culture medium. The phage fraction was diluted with TBS to prepare a phage library solution. Then, BSA and CaCl₂ were added the phage library solution at final concentrations of 4% BSA and 1.2 mM calcium ion concentration, respectively. The panning method used was a conventional panning method using antigen-immobilized magnetic beads (J. Immunol. Methods. (2008) 332(1-2): 2-9; J. Immunol. Methods. (2001) 247(1-2): 191-203; Biotechnol. Prog. (2002) 18(2): 212-20; Mol. Cell Proteomics (2003) 2(2): 61-9). The magnetic beads used were NeutrAvidin-coated beads (Sera-Mag SpeedBeads NeutrAvidin-coated) and Streptavidin-coated beads (Dynabeads M-280 Streptavidin).

Specifically, 250 μmol of the biotin-labeled antigen was added to the prepared phage library solution. Thus, the solution was contacted with the antigen at room temperature for 60 minutes. Magnetic beads blocked with BSA were added, and the antigen-phage complex was allowed to bind to the magnetic beads at room temperature for 15 minutes. The beads were washed three times with 1.2 mM CaCl₂/TBST (TBST containing 1.2 mM CaCl₂), and then twice with 1 ml of 1.2 mM CaCl₂/TBS (TBS containing 1.2 mM CaCl₂). Thereafter, 0.5 ml of 1 mg/ml trypsin was added to the beads. After 15 minutes of dispersion at room temperature, the beads were immediately separated using a magnetic stand to collect a phage solution. The prepared phage solution was added to 10 ml of E. coli of stain TG1 at the logarithmic growth phase (OD600=0.4 to 0.7). The E. coli was cultured with gentle stirring at 37° C. for one hour to infect the phages. The infected E. coli was seeded in a plate (225 mm×225 mm). Then, phages were collected from the culture medium of the seeded E. coli to prepare a phage library solution.

In the second round and subsequent panning, phages were enriched using the Ca-dependent binding activity as an indicator. Specifically, 40 μmol of the biotin-labeled antigen was added to the prepared phage library solution. Thus, the phage library was contacted with the antigen at room temperature for 60 minutes. Magnetic beads blocked with BSA were added, and the antigen-phage complex was allowed to bind to the magnetic beads at room temperature for 15 minutes. The beads were washed with 1 ml of 1.2 mM CaCl₂/TBST and 1.2 mM CaCl₂/TBS. Next, 0.1 ml of 2 mM EDTA/TBS was added to the beads. After dispersion at room temperature, the beads were immediately separated using a magnetic stand to collect a phage solution. The pIII protein (helper phage-derived protein pIII) was cleaved from phages that did not display Fab by adding 5 μl of 100 mg/ml trypsin to the collected phage solution to eliminate the ability of phages displaying no Fab to infect E. coli. Phages collected from the trypsinized phage solution were added to 10 ml of E. coli cells of the TG1 strain at the logarithmic growth phase (OD600=0.4 to 0.7). The E. coli was cultured while gently stirring at 37° C. for one hour to infect phage. The infected E. coli was seeded in a plate (225 mm×225 mm). Then, phages were collected from the culture medium of the seeded E. coli to prepare a phage library solution. Panning was performed three times using the Ca-dependent binding activity as an indicator.

(29-3) Assessment by Phage ELISA

Culture supernatants containing phages were collected from single colonies of E. coli obtained by the method described above according to a conventional method (Methods Mol. Biol. (2002) 178, 133-145).

BSA and CaCl₂ were added at final concentrations of 4% BSA and 1.2 mM calcium ion concentration, respectively, to the phage-containing culture supernatants. The supernatants were subjected to ELISA by the following procedure. A StreptaWell 96-well microtiter plate (Roche) was coated overnight with 100 μl of PBS containing the biotin-labeled antigen. The antigen was removed by washing each well of the plate with PBST. Then, the wells were blocked with 250 μl of 4% BSA-TBS for one hour or more. After removal of 4% BSA-TBS, the prepared culture supernatants were added to the each well. The plate was incubated at 37° C. for one hour so that the antibody-displaying phages were allowed to bind to the antigen on each well. After each well was washed with 1.2 mM CaCl₂/TBST, 1.2 mM CaCl₂/TBS or 1 mM EDTA/TBS was added. The plate was left for incubation at 37° C. for 30 minutes. After washing with 1.2 mM CaCl₂/TBST, an HRP-conjugated anti-M13 antibody (Amersham Pharmacia Biotech) diluted with TBS containing BSA and calcium ion at final concentrations of 4% BSA and 1.2 mM calcium ion concentration was added to each well, and the plate was incubated for one hour. After washing with 1.2 mM CaCl₂/TBST, the TMB single solution (ZYMED) was added to each well. The chromogenic reaction in the solution of each well was stopped by adding sulfuric acid. Then, the developed color was assessed by measuring absorbance at 450 nm.

From the isolated 96 clones, antibody 6KC4-1#85 having Ca-dependent IL-6-binding activity was obtained by phage ELISA. Using antibody fragments that were predicted to have a Ca-dependent antigen-binding activity based on the result of the phage ELISA described above as a template, genes were amplified with specific primers and their sequences were analyzed. The heavy-chain and light-chain variable region sequences of antibody 6KC4-1#85 are shown in SEQ ID NOs: 119 and 120, respectively. The polynucleotide encoding the heavy-chain variable region of antibody 6KC4-1#85 (SEQ ID NO: 119) was linked to a polynucleotide encoding an IgG1-derived sequence by PCR method. The resulting DNA fragment was inserted into an animal cell expression vector to construct an expression vector for the heavy chain of SEQ ID NO: 121. A polynucleotide encoding the light-chain variable region of antibody 6KC4-1 #85 (SEQ ID NO: 120) was linked to a polynucleotide encoding the constant region of the natural Kappa chain (SEQ ID NO: 54) by PCR. The linked DNA fragment was inserted into an animal cell expression vector. Sequences of the constructed variants were confirmed by a method known to those skilled in the art.

(29-4) Expression and Purification of Antibodies

Clone 6KC4-1#85 that was predicted to have a Ca-dependent antigen-binding activity based on the result of phage ELISA was inserted into animal cell expression plasmids. Antibody expression was carried out by the following method. Cells of human fetal kidney cell-derived FreeStyle 293-F (Invitrogen) were suspended in the FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 1.33×10⁶ cells/ml (3 ml) into each well of a 6-well plate. The prepared plasmids were introduced into cells by a lipofection method. The cells are cultured for four days in a CO₂ incubator (37° C., 8% CO₂, 90 rpm). From the culture supernatants, antibodies were purified using the rProtein A Sepharose™ Fast Flow (Amersham Biosciences) by a method known to those skilled in the art. Absorbance at 280 nm of the purified antibody solutions was measured using a spectrophotometer. Antibody concentrations were calculated from the determined values using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4: 2411-2423).

Reference Example 30 Assessment of Antibody 6KC4-1#85 for Calcium Ion Binding

Calcium-dependent antigen-binding antibody 6KC4-1#85 which was isolated from a human antibody library was assessed for its calcium binding. Whether the measured Tm value varies depending on the ionized calcium concentration condition was assessed according to the method described in Reference Example 27.

Tm values for the Fab domain of antibody 6KC4-1#85 are shown in Table 42. As shown in Table 42, the Tm value of the 6KC4-1#85 antibody Fab domain varied depending on the calcium ion concentration. This demonstrates that antibody 6KC4-1#85 binds to calcium.

TABLE 42 CALCIUM ION CONCENTRATION ΔTm (° C.) ANTIBODY 3 μM 2 mM 2 mM − 3 μM 6KC4-1#85 71.49 75.39 3.9

Reference Example 31 Identification of Calcium Ion-Binding Site in Antibody 6KC4-1#85

As demonstrated in Reference Example 30, antibody 6KC4-1#85 binds to calcium ion. However, 6KC4-1#85 does not have a calcium-binding motif such as the hVk5-2 sequence which was revealed from assessment to have a calcium-binding motif. Then, whether calcium ion binds to either or both of the heavy chain and the light chain of antibody 6KC4-1#85 was confirmed by assessing the calcium ion binding of altered antibodies resulting from exchanging the heavy chain and light chain of 6KC4-1#85 respectively with those of an anti-glypican 3 antibody (heavy chain sequence GC_H (SEQ ID NO: 55), light chain sequence GC_L (SEQ ID NO: 56)) which does not bind calcium ion. The Tm values of altered antibodies measured according to the method described in Reference Example 27 are shown in Table 43. The result suggests that the heavy chain of antibody 6KC4-1#85 binds to calcium, because the Tm values of the altered antibody having the heavy chain of antibody 6KC4-1#85 changed depending on calcium ion concentration.

TABLE 43 ΔTm CALCIUM ION (° C.) CONCENTRATION 2 mM − HEAVY CHAIN LIGHT CHAIN 3 μm 2 mM 3 μM 6KC4-1#85 6KC4-1#85 71.46 75.18 3.72 6KC4-1#85 GC_L 78.87 80.01 1.14 GC_H 6KC4-1#85 75.69 75.94 0.25 GC_H GC_L 79.94 80.01 0.07

Thus, to further identify residues responsible for the calcium ion binding of the heavy chain of antibody 6KC4-1#85, altered heavy chains (6_H1-11 (SEQ ID NO: 126), 6_H1-12 (SEQ ID NO: 127), 6_H1-13 (SEQ ID NO: 128), 6_H1-14 (SEQ ID NO: 129), 6_H1-15 (SEQ ID NO: 130)) or altered light chains (6_L1-5 (SEQ ID NO: 131) and 6_L1-6 (SEQ ID NO: 132)) were constructed by substituting an Asp (D) residue in the CDR of antibody 6KC4-1 #85 with an Ala (A) residue which does not participate in the binding or chelation of calcium ion. By the method described in Reference Example 29, altered antibodies were purified from the culture media of animal cells introduced with expression vectors carrying the altered antibody genes. The purified altered antibodies were assessed for their calcium binding according to the method described in Reference Example 27. The measurement result is shown in Table 44. As shown in Table 44, substitution of an Ala residue for the residue at position 95 or 101 (Kabat numbering) in the heavy chain CDR3 of antibody 6KC4-1#85 resulted in loss of the calcium-binding activity of antibody 6KC4-1#85. This suggests that these residues are responsible for calcium binding. The calcium-binding motif located at the base of the CDR3 loop in the heavy chain of antibody 6KC4-1#85, which was found based on the calcium binding capacity of the antibody altered from antibody 6KC4-1#85, can be a new factor for designing Ca libraries which are used to obtain antigen-binding domains whose antigen-binding activity changes depending on calcium ion concentration and which are to be contained in antigen-binding molecules of the present invention. In Reference Examples 38 and 39 below, calcium-binding motifs were introduced into the light chain variable region. Meanwhile, such libraries include, for example, those containing the heavy chain CDR3 from antibody 6KC4-1 #85 and flexible residues in the CDRs other than the heavy chain CDR3 but including the light chain CDRs.

TABLE 44 CALCIUM ION CONCENTRATION ΔTm (° C.) HEAVY CHAIN LIGHT CHAIN ALTERED RESIDUE 3 μM 2 mM 2 mM-3 μM 6KC4-1#85 6KC4-1#85 WILD-TYPE 71.49 75.39 3.9 6H1-11 6KC4-1#85 H CHAIN POSITION 71.73 75.56 3.83 61 (Kabat NUMBERING) 6H1-12 6KC4-1#85 H CHAIN POSITION 72.9 73.43 0.53 95 (Kabat NUMBERING) 6H1-13 6KC4-1#85 H CHAIN POSITION 70.94 76.25 5.31 100a (Kabat NUMBERING) 6H1-14 6KC4-1#85 H CHAIN POSITION 73.95 75.14 1.19 100g (Kabat NUMBERING) 6H1-15 6KC4-1#85 H CHAIN POSITION 65.37 66.25 0.87 101 (Kabat NUMBERING) 6KC4-1#85 6L1-5 L CHAIN POSITION 71.92 76.08 4.16 50 (Kabat NUMBERING) 6KC4-1#85 6L1-6 L CHAIN POSITION 72.13 78.74 6.61 92 (Kabat NUMBERING)

Reference Example 32 Examination of Effects of Ca-Dependent Binding Antibody on Plasma Retention of Antigen Using Normal Mice (32-1) In Vivo Test Using Normal Mice

To a normal mouse (C57BL/6J mouse, Charles River Japan), hsIL-6R (soluble human IL-6 receptor prepared in Reference Example 3) alone was administered, or hsIL-6R and anti-human IL-6 receptor antibody were administered simultaneously to examine the kinetics of the hsIL-6R and anti-human IL-6 receptor antibody in vivo. A single dose (10 mL/kg) of the hsIL-6R solution (5 μg/mL) or a mixture of hsIL-6R and anti-human IL-6 receptor antibody was administered into the tail vein. The above H54/L28-IgG1, 6RL#9-IgG1, and FH4-IgG1 were used as anti-human IL-6 receptor antibodies.

The hsIL-6R concentration in all the mixtures is 5 μg/mL. The concentrations of anti-human IL-6 receptor antibody vary with the antibodies: 0.1 mg/mL for H54/L28-IgG1 and 10 mg/mL for 6RL#9-IgG1 and FH4-IgG1. At this time, it was thought that most of the hsIL-6Rs bind to the antibody because the anti-human IL-6 receptor antibody exists in a sufficient or excessive amount for hsIL-6R. Blood samples were collected at 15 minutes, 7 hours and 1, 2, 4, 7, 14, 21, and 28 days after the administration. The blood samples obtained were immediately centrifuged for 15 minutes at 4° C. and 12,000 rpm to separate plasma. The separated plasma was stored in a freezer set to −20° C. or lower until the time of measurement.

(32-2) Determination of Plasma Anti-Human IL-6 Receptor Antibody Concentration in Normal Mice by ELISA

The plasma concentration of anti-human IL-6 receptor antibody in a mouse was determined by ELISA. First, Anti-Human IgG (γ-chain specific) F(ab′)2 Fragment of Antibody (SIGMA) was dispensed into a Nunc-Immuno Plate, MaxiSorp (Nalge Nunc International), and was allowed to stand undisturbed overnight at 4° C. to prepare an anti-human IgG-immobilized plate. Calibration curve samples at a plasma concentration of 0.64, 0.32, 0.16, 0.08, 0.04, 0.02, or 0.01 μg/mL, and mouse plasma measurement samples diluted by 100-fold or above were each dispensed into the anti-human IgG-immobilized plate, followed by incubation for 1 hour at 25° C. Subsequently, the plate was allowed to react with a biotinylated anti-human IL-6 R antibody (R&D) for 1 hour at 25° C., followed by reaction with Streptavidin-PolyHRP80 (Stereospecific Detection Technologies) for 0.5 hours at 25° C. The chromogenic reaction was conducted using TMB One Component HRP Microwell Substrate (BioFX Laboratories) as a substrate. After the chromogenic reaction was stopped by adding 1N-sulfuric acid (Showa Chemical), absorbance at 450 nm of the colored solution was measured using a microplate reader. The plasma concentration in the mouse was calculated from the absorbance of the calibration curve using the SOFTmax PRO analysis software (Molecular Devices). Changes in the plasma concentrations of antibodies, H54/L28-IgG1, 6RL#9-IgG1, and FH4-IgG1, in the normal mice after intravenous administration, measured as described above, are shown in FIG. 55.

(32-3) Determination of Plasma hsIL-6R Concentration by an Electrochemiluminescence Method

The plasma concentration of hsIL-6R in a mouse was determined by an electrochemiluminescence method. A hsIL-6R calibration curve sample prepared at 2,000, 1,000, 500, 250, 125, 62.5, or 31.25 pg/mL, and a mouse plasma measurement sample diluted by 50-fold or above, were mixed with a monoclonal anti-human IL-6R antibody (R&D) ruthenated with SULFO-TAG NHS Ester (Meso Scale Discovery), a biotinylated anti-human IL-6 R antibody (R&D), and tocilizumab (heavy chain SEQ ID NO: 111, light chain SEQ ID NO: 112), followed by overnight reaction at 4° C. At that time, the assay buffer contained 10 mM EDTA to reduce the free Ca concentration in the sample and dissociate almost all the hsIL-6Rs in the sample from 6RL#9-IgG1 or FH4-IgG1 to be bound to the added tocilizumab. Subsequently, said reaction solution was dispensed into an MA400 PR Streptavidin Plate (Meso Scale Discovery). In addition, after washing each well of the plate that was allowed to react for 1 hour at 25° C. Read Buffer T (×4) (Meso Scale Discovery) was dispensed into each well. Immediately, the reaction solution was subjected to measurement using a SECTOR PR 400 reader (Meso Scale Discovery). The concentration of hsIL-6R was calculated from the response of the calibration curve using the SOFTmax PRO analysis software (Molecular Devices). Changes in the plasma concentration of hsIL-6R in the normal mouse after intravenous administration, determined as described above, are shown in FIG. 56.

As a result, the disappearance of hsIL-6R was very rapid when hsIL-6R was administered alone, while the disappearance of hsIL-6R was significantly delayed when hsIL-6R was administered simultaneously with H54/L28-IgG1, a conventional antibody having no Ca-dependent binding ability to soluble human IL-6 receptor. In contrast, the disappearance of hsIL-6R was significantly accelerated when hsIL-6R was administered simultaneously with 6RL#9-IgG1 or FH4-IgG1 having 100-fold or higher Ca-dependent binding ability to hsIL-6R. The plasma concentrations of hsIL-6R one day after soluble human IL-6 receptor was administered simultaneously with 6RL#9-IgG1 and FH4-IgG1 were reduced 39-fold and 2-fold, respectively, as compared with simultaneous administration with H54/L28-IgG1. Thus, the calcium-dependent binding antibodies were confirmed to be able to accelerate antigen disappearance from the plasma.

Reference Example 33 Exploration of Human Germline Sequences that Bind to Calcium Ion

(33-1) Antibody that Binds to Antigen in a Calcium-Dependent Manner

Antibodies that bind to an antigen in a calcium-dependent manner (calcium-dependent antigen-binding antibodies) are those whose interactions with antigen change with calcium concentration. A calcium-dependent antigen-binding antibody is thought to bind to an antigen through calcium ion. Thus, amino acids that form an epitope on the antigen side are negatively charged amino acids that can chelate calcium ions or amino acids that can be a hydrogen-bond acceptor. These properties of amino acids that form an epitope allows targeting of an epitope other than antigen-binding molecules, which are generated by introducing histidines and bind to an antigen in a pH-dependent manner. Furthermore, the use of antigen-binding molecules having calcium- and pH-dependent antigen-binding properties is thought to allow the formation of antigen-binding molecules that can individually target various epitopes having broad properties. Thus, if a population of molecules containing a calcium-binding motif (Ca library) is constructed, from which antigen-binding molecules are obtained, calcium-dependent antigen-binding molecules are thought to be effectively obtained.

(33-2) Acquisition of Human Germline Sequences

An example of the population of molecules containing a calcium-binding motif is an example in which said molecules are antibodies. In other words, an antibody library containing a calcium-binding motif may be a Ca library.

Calcium ion-binding antibodies containing human germline sequences have not been reported. Thus, each antibody having human germline sequences were cloned using as a template cDNA prepared from Human Fetal Spleen Poly RNA (Clontech) to assess whether antibodies having human germline sequences bind to calcium ion. Cloned DNA fragments were inserted into animal cell expression vectors. The nucleotide sequences of the constructed expression vectors were determined by a method known to those skilled in the art. The SEQ IDs are shown in Table 45. By PCR, polynucleotides encoding SEQ ID NO: 58 (Vk1), SEQ ID NO: 59 (Vk2), SEQ ID NO: 60 (Vk3), SEQ ID NO: 61 (Vk4), and SEQ ID NO: 62 (Vk5-2) were linked to a polynucleotide encoding the natural Kappa chain constant region (SEQ ID NO: 54). The linked DNA fragments were inserted into animal cell expression vectors. Furthermore, heavy chain variable region polynucleotides encoding SEQ ID NO: 63, SEQ ID NO: 64, SEQ ID NO: 65, SEQ ID NO: 66, and SEQ ID NO: 67 were linked by PCR to a polynucleotide encoding an IgG1 of SEQ ID NO: 53 (having a deletion of two amino acids at the C terminus of natural sequence). The resulting DNA fragments were inserted into animal cell expression vectors. The sequences of the constructed variants were confirmed by a method known to those skilled in the art.

TABLE 45 LIGHT CHAIN HEAVY CHAIN LIGHT CHAIN GERMLINE (VARIABLE REGION) VARIABLE REGION SEQUENCE SEQ ID NO SEQ ID NO Vk1 63 58 Vk2 64 59 Vk3 65 60 Vk4 66 61 Vk5 67 62

(33-3) Expression and Purification of Antibodies

The constructed animal cell expression vectors inserted with the DNA fragments having the five types of human germline sequences were introduced into animal cells. Antibody expression was carried out by the following method. Cells of human fetal kidney cell-derived FreeStyle 293-F (Invitrogen) were suspended in the FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 1.33×10⁶ cells/ml (3 ml) into each well of a 6-well plate. The prepared plasmids are introduced into cells by a lipofection method. The cells were cultured for four days in a CO₂ incubator (37° C., 8% CO₂, 90 rpm). From the culture supernatants prepared as described above, antibodies were purified using the rProtein A Sepharose™ Fast Flow (Amersham Biosciences) by a method known to those skilled in the art. Absorbance at 280 nm of the purified antibody solutions was measured using a spectrophotometer. Antibody concentrations were calculated from the determined values using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4: 2411-2423).

(33-4) Assessment of Antibodies Having Human Germline Sequences for their Calcium Ion-Binding Activity

The purified antibodies were assessed for their calcium ion-binding activity. The intermediate temperature of thermal denaturation (Tm value) was measured by differential scanning calorimetry (DSC) as an indicator for examining calcium ion binding to the antibody (MicroCal VP-Capillary DSC, MicroCal). The intermediate temperature of thermal denaturation (Tm value) is an indicator of stability. It becomes higher when a protein is stabilized through calcium ion binding, as compared with the case where no calcium ion is bound (J. Biol. Chem. (2008) 283, 37, 25140-25149). The binding activity of calcium ion to antibody was evaluated by examining changes in the Tm value of the antibody depending on the changes in the calcium ion concentration in the antibody solution. The purified antibody was subjected to dialysis (EasySEP, TOMY) using an external solution of 20 mM Tris-HCl, 150 mM NaCl, and 2 mM CaCl₂ (pH 7.4) or 20 mM Tris-HCl, 150 mM NaCl, and 3 μM CaCl₂ (pH 7.4). DSC measurement was conducted at a heating rate of 240° C./hr from 20 to 115° C. using as a test substance an antibody solution prepared at about 0.1 mg/mL with the dialysate. The intermediate temperatures of thermal denaturation (Tm values) of the Fab domains of each antibody, calculated from the denaturation curve obtained by DSC, are shown in Table 46.

TABLE 46 CALCIUM ION LIGHT CHAIN CONCENTRATION ΔTm (° C.) GERMLINE SEQUENCE 3 μM 2 mM 2 mM-3 μM hVk1 80.32 80.78 0.46 hVk2 80.67 80.61 −0.06 hVk3 81.64 81.36 −0.28 hVk4 70.74 70.74 0 hVk5 71.52 74.17 2.65

The result showed that the Tm values of the Fab domains of antibodies having the hVk1, hVk2, hVk3, or hVk4 sequence did not vary depending on the calcium ion concentration in the Fab domain-containing solutions. Meanwhile, the Tm value for the antibody Fab domain having the hVk5 sequence varied depending on the calcium ion concentration in the Fab domain-containing solution. This demonstrates that the hVk5 sequence binds to calcium ion.

(33-5) Assessment of hVk5-2 Sequence for Calcium Binding

In (33-2), Vk5-2 variant 1 (SEQ ID NO: 68) and Vk5-2 variant 2 (SEQ ID NO: 69) were obtained in addition to Vk5-2 (SEQ ID NO: 57), all of which are classified as Vk5-2. These variants were assessed for their calcium binding. DNA fragments for Vk5-2. Vk5-2 variant 1, and Vk5-2 variant 2 were each inserted into animal cell expression vectors. The nucleotide sequences of the constructed expression vectors were determined by a method known to those skilled in the art. By the method described in (33-3), the animal cell expression vectors inserted with DNA fragments for Vk5-2, Vk5-2 variant 1, and Vk5-2 variant 2 were introduced, in combination with animal expression vector carrying an insert to express CIM_H (SEQ ID NO: 67) as a heavy chain, into animal cells and antibodies were purified. The purified antibodies were assessed for their calcium ion-binding activity. The purified antibodies were dialyzed (EasySEP, TOMY) against 20 mM Tris-HCl/150 mM NaCl (pH 7.5) (in Table 47, indicated as 0 mM calcium ion concentration) or 20 mM Tris-HCl/150 mM NaCl/2 mM CaCl₂ (pH 7.5). DSC measurement was carried out at a rate of temperature increase of 240° C./hr from 20 to 115° C. using as a test substance an antibody solution prepared at a concentration of about 0.1 mg/mL with the same solution as used for dialysis. Based on the obtained DSC denaturation curve, the intermediate temperature of thermal denaturation (Tm value) was calculated for the Fab domain of each antibody. The Tm values are shown in Table 47.

TABLE 47 CALCIUM ION CONCENTRATION ΔTm (° C.) LIGHT CHAIN 0 mM 2 mM 2 mM-0 mM Vk5-2 71.65 74.38 2.73 Vk5-2 VARIANT 1 65.75 72.24 6.49 Vk5-2 VARIANT 2 66.46 72.24 5.78

The result showed that the Tm value for the Fab domains of antibodies having the sequence of Vk5-2, Vk5-2 variant 1, or Vk5-2 variant 2 varied depending on the calcium ion concentration in solutions containing antibodies having the Fab domains. This demonstrates that antibodies having a sequence classified as Vk5-2 bind to calcium ion.

Reference Example 34 Assessment of the Human Vk5 (hVk5) Sequence

(34-1) hVk5 Sequence

The only hVk5 sequence registered in Kabat database is hVk5-2 sequence. Herein, hVk5 and hVk5-2 are used synonymously. WO2010/136598 discloses that the abundance ratio of the hVk5-2 sequence in the germline sequence is 0.4%. Other reports have been also made in which the abundance ratio of the hVk5-2 sequence in the germline sequence is 0-0.06% (J. Mol. Biol. (2000) 296, 57-86; Proc. Natl. Acad. Sci. USA (2009) 106, 48, 20216-20221). As described above, since the hVk5-2 sequence is a sequence of low appearance frequency in the germline sequence, it was thought to be inefficient to obtain a calcium-binding antibody from an antibody library consisting of human germline sequences or B cells obtained by immunizing a mouse expressing human antibodies. Thus, it is possible to design Ca libraries containing the sequence of human hVk5-2. Meanwhile, reported synthetic antibody libraries (WO2010/105256 and WO2010/136598) did not contain the sequence of hVk5. In addition, realization of the possibility is unknown because no report has been published on the physical properties of the hVk5-2 sequence.

(34-2) Construction, Expression, and Purification of a Non-Glycosylated Form of the hVk5-2 Sequence

The hVk5-2 sequence has a sequence for N-type glycosylation at position 20 amino acid (Kabat numbering). Sugar chains attached to proteins exhibit heterogeneity. Thus, it is desirable to lose the glycosylation from the viewpoint of substance homogeneity. In this context, variant hVk5-2_L65 (SEQ ID NO: 70) in which the Asn (N) residue at position 20 (Kabat numbering) is substituted with Thr (T) was constructed. Amino acid substitution was carried out by a method known to those skilled in the art using the QuikChange Site-Directed Mutagenesis Kit (Stratagene). A DNA encoding the variant hVk5-2_L65 was inserted into an animal expression vector. The animal expression vector inserted with the constructed DNA encoding variant hVk5-2_L65, in combination with an animal expression vector having an insert to express CIM_H (SEQ ID NO: 67) as a heavy chain, was introduced into animal cells by the method described in Reference Example 25. The antibody comprising hVk5-2_L65 and CIM_H, which was expressed in animal cells introduced with the vectors, was purified by the method described in Reference Example 33.

(34-3) Assessment of the Antibody Having the Non-Glycosylated hVk5-2 Sequence for Physical Properties

The isolated antibody having the modified sequence hVk5-2_L65 was analyzed by ion-exchange chromatography to test whether it is less heterogeneous than the antibody having the original sequence hVk5-2 before alteration. The procedure of ion-exchange chromatography is shown in Table 48. The analysis result showed that hVk5-2_L65 modified at the glycosylation site was less heterogeneous than the original sequence hVk5-2, as shown in FIG. 57.

TABLE 48 CONDITION COLUMN TOSOH TSKgel DEAE-NPR MOBILE PHASE A; 10 mM Tris-HCl, 3 μM CaCl₂ (pH 8.0) B; 10 mM Tris-HCl, 500 mM NaCl, 3 μM CaCl₂ (pH 8.0) GRADIENT SCHEDULE % B = 0 − (5 min) − 0 − 2%/1 min COLUMN TEMPERATURE 40° C. DETECTION 280 nm INJECTION VOLUME 100 μL (5 μg)

Next, whether the less-heterogeneous hVk5-2_L65 sequence-comprising antibody binds to calcium ion was assessed by the method described in Reference Example 33. The result showed that the Tm value for the Fab domain of the antibody having hVk5-2_L65 with altered glycosylation site also varied depending on the calcium ion concentration in the antibody solutions, as shown in Table 49. Specifically, it was demonstrated that the Fab domain of the antibody having hVk5-2_L65 with altered glycosylation site binds to calcium ion.

TABLE 49 GLYCOSYL- CALCIUM ION LIGHT ATED CONCENTRATION ΔTm (° C.) CHAIN SEQUENCE 3 μM 2 mM 2 mM-3 μM hVk5-2 YES 71.52 74.17 2.65 hVk5-2_L65 NO 71.51 73.66 2.15

Reference Example 35 Assessment of the Calcium Ion-Binding Activity of Antibody Molecules Having CDR Sequence of the hVk5-2 Sequence

(35-1) Construction, Expression, and Purification of Modified Antibodies Having a CDR Sequence from the hVk5-2 Sequence

The hVk5-2_L65 sequence is a sequence with altered amino acids at a glycosylation site in the framework of human Vk5-2 sequence. As described in Reference Example 34, it was demonstrated that calcium ion bound even after alteration of the glycosylation site. Meanwhile, from the viewpoint of immunogenicity, it is generally desirable that the framework sequence is a germline sequence. Thus, the present inventors assessed whether an antibody framework sequence could be substituted with the framework sequence of a non-glycosylated germline sequence while maintaining the calcium ion-binding activity of the antibody.

Polynucleotides encoding chemically synthesized sequences in which framework sequence of the hVk5-2 sequence is altered with hVk1, hVk2, hVk3, or hVk4 (CaVk1 (SEQ ID NO: 71), CaVk2 (SEQ ID NO: 72), CaVk3 (SEQ ID NO: 73), or CaVk4 (SEQ ID NO: 74), respectively) were linked by PCR to a polynucleotide encoding the constant region (SEQ ID NO: 54) of the natural Kappa chain. The linked DNA fragments were inserted into animal cell expression vectors. Sequences of the constructed variants were confirmed by a method known to those skilled in the art. Each plasmid constructed as described above was introduced into animal cells in combination with a plasmid inserted with a polynucleotide encoding CIM_H (SEQ ID NO: 67) by the method described in Reference Example 33. The expressed antibody molecules of interest were purified from culture media of the animal cells introduced with the plasmids.

(35-2) Assessment of Altered Antibodies Having the CDR Sequence of the hVk5-2 Sequence for their Calcium Ion-Binding Activity

Whether calcium ion binds to altered antibodies having the CDR sequence of the hVK5-2 sequence and the framework sequences of germline sequences other than hVk5-2 (hVk1, hVk2, hVk3, and hVk4) was assessed by the method described in Reference Example 25. The assessment result is shown in Table 50. The Tm value of the Fab domain of each altered antibody was revealed to vary depending on the calcium ion concentration in the antibody solutions. This demonstrates that antibodies having a framework sequence other than the hVk5-2 sequence also bind to calcium ion.

TABLE 50 GERMLINE (LIGHT CHAIN CALCIUM ION FRAMEWORK CONCENTRATION ΔTm (° C.) SEQUENCE) 3 μM 2 mM 2 mM-3 μM hVk1 77.51 79.79 2.28 hVk2 78.46 80.37 1.91 hVk3 77.27 79.54 2.27 hVk4 80.35 81.38 1.03 hVk5-2 71.52 74.17 2.65

The thermal denaturation temperature (Tm value), as an indicator of thermal stability, of the Fab domain of each antibody altered to have the CDR sequence of the hVK5-2 sequence and the framework sequence of a germline sequence other than the hVk5-2 sequence (hVk1, hVk2, hVk3, or hVk4) was demonstrated to be greater than that of the Fab domain of the original antibody having the hVk5-2 sequence. This result shows that antibodies having the CDR sequence of the hVk5-2 sequence and the framework sequence of hVk1, hVk2, hVk3, or hVk4 not only have calcium ion-binding activity but also are excellent molecules from the viewpoint of thermal stability.

Reference Example 36 Identification of the Calcium Ion-Binding Site in Human Germline hVk5-2 S

(36-1) Design of Mutation Site in the CDR Sequence of the hVk5-2 Sequence

As described in Reference Example 35, antibodies having the light chain resulting from introduction of the CDR sequence of the hVk5-2 sequence into the framework sequence of a different germline sequence were also demonstrated to bind to calcium ion. This result suggests that in hVk5-2 a calcium ion-binding site is localized within its CDR sequence. Amino acids that bind to calcium ion, i.e., chelate calcium ion, include negatively charged amino acids and amino acids that can be a hydrogen bond acceptor. Thus, it was tested whether antibodies having a mutant hVk5-2 sequence with a substitution of an Ala (A) residue for an Asp (D) or Glu (E) residue in the CDR sequence of the hVk5-2 sequence bind to calcium ion.

(36-2) Construction of Variant hVk5-2 Sequences with Ala Substitution, and Expression and Purification of Antibodies

Antibody molecules were prepared to comprise a light chain with substitution of an Ala residue for Asp and/or Glu residue in the CDR sequence of the hVk5-2 sequence. As described in Reference Example 34, non-glycosylated variant hVk5-2_L65 exhibited calcium ion binding and was assumed to be equivalent to the hVk5-2 sequence in terms of calcium ion binding. In this Example, amino acid substitutions were introduced into hVk5-2_L65 as a template sequence. Constructed variants are shown in Table 51. Amino acid substitutions were carried out by methods known to those skilled in the art such as using the QuikChange Site-Directed Mutagenesis Kit (Stratagene), PCR, or the In fusion Advantage PCR Cloning Kit (TAKARA) to construct expression vectors for altered light chains having an amino acid substitution.

TABLE 51 LIGHT CHAIN ALTERED POSITION VARIANT NAME (Kabat NUMBERING) SEQ ID NO hVk5-2_L65 WILDTYPE 70 hVk5-2_L66 30 75 hVk5-2_L67 31 76 hVk5-2_L68 32 77 hVk5-2_L69 50 78 hVk5-2_L70 30, 32 79 hVk5-2_L71 30, 50 80 hVk5-2_L72 30, 32, 50 81 hVk5-2_L73 92 82

Nucleotide sequences of the constructed expression vectors were confirmed by a method known to those skilled in the art. The expression vectors constructed for the altered light chains were transiently introduced, in combination with an expression vector for the heavy chain CIM_H (SEQ ID NO: 67), into cells of the human fetal kidney cell-derived HEK293H line (Invitrogen) or FreeStyle293 (Invitrogen) to express antibodies. From the obtained culture supernatants, antibodies were purified using the rProtein A Sepharose™ Fast Flow (GE Healthcare) by a method known to those skilled in the art. Absorbance at 280 nm of the purified antibody solutions was measured using a spectrophotometer. Antibody concentrations were calculated from the determined values using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4: 2411-2423).

(36-3) Assessment of the Calcium Ion-Binding Activity of Antibodies Having an Ala Substitution in the hVk5-2 Sequence

Whether the obtained purified antibodies bind to calcium ion was tested by the method described in Reference Example 33. The result is shown in Table 52. Some antibodies having substitution of an Asp or Glu residue in the CDR sequence of the hVk5-2 sequence with an Ala residue which cannot be involved in calcium ion binding or chelation were revealed to have an Fab domain whose Tm did not vary by the calcium ion concentration in the antibody solutions. The substitution sites at which Ala substitution did not alter the Tm (positions 32 and 92 (Kabat numbering)) were demonstrated to be greatly important for the calcium ion-antibody binding.

TABLE 52 ALTERED LIGHT CHAIN POSITION CALCIUM ION VARIANT (Kabat CONCENTRATION ΔTm (° C.) NAME NUMBERING) 0 μM 2 mM 2 mM-0 μM hVk5-2_L65 WILDTYPE 71.71 73.69 1.98 hVk5-2_L66 30 71.65 72.83 1.18 hVk5-2_L67 31 71.52 73.30 1.78 hVk5-2_L68 32 73.25 74.03 0.78 hVk5-2_L69 50 72.00 73.97 1.97 hVk5-2_L70 30, 32 73.42 73.60 0.18 hVk5-2_L71 30, 50 71.84 72.57 0.73 hVk5-2_L72 30, 32, 50 75.04 75.17 0.13 hVk5-2_L73 92 75.23 75.04 −0.19

Reference Example 37 Assessment of the Antibodies Having hVk1 Sequence with Calcium Ion-Binding Motif

(37-1) Construction of an hVk1 Sequence with Calcium Ion-Binding Motif, and Expression and Purification of Antibodies

The result described in Reference Example 36 on the calcium-binding activity of the Ala substitute demonstrates that Asp or Glu residues in the CDR sequence of the hVk5-2 sequence were important for calcium binding. Thus, the present inventors assessed whether an antibody can bind to calcium ion when the residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) alone were introduced into a different germline variable region sequence. Specifically, variant LfVk1_Ca (SEQ ID NO: 83) was constructed by substituting the residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) in the hVk5-2 sequence for the residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) in the hVk1 sequence (a human germline sequence). Specifically, it was tested whether antibodies having an hVk1 sequence introduced with only 5 residues from the hVk5-2 sequence can bind to calcium. The variants were produced by the same method as described in Reference Example 36. The resulting light chain variant LfVk1_Ca and LfVk1 having the light-chain hVk1 sequence (SEQ ID NO: 84) were co-expressed with the heavy chain CIM_H (SEQ ID NO: 67). Antibodies were expressed and purified by the same method as described in Reference Example 36.

(37-2) Assessment of the Calcium Ion-Binding Activity of Antibodies Having a Human hVk1 Sequence with Calcium Ion-Binding Motif

Whether the purified antibody prepared as described above binds to calcium ion was assessed by the method described in Reference Example 33. The result is shown in Table 53. The Tm value of the Fab domain of the antibody having LfVk1 with an hVk1 sequence did not vary depending on the calcium concentration in the antibody solutions. Meanwhile, Tm of the antibody having the LfVk1_Ca sequence was shifted by 1° C. or more upon change in the calcium concentration in the antibody solutions. Thus, it was shown that the antibody having LfVk1_Ca binds to calcium. The result described above demonstrates that the entire CDR sequence of hVk5-2 is not required, while the residues introduced for construction of the LfVk1_Ca sequence alone are sufficient for calcium ion binding.

TABLE 53 CALCIUM ION LIGHT CHAIN CONCENTRATION ΔTm (° C.) VARIANT 3 μM 2 mM 2 mM-3 μM LfVk1 83.18 83.81 0.63 LfVk1_Ca 79.83 82.24 2.41

(37-3) Construction, Expression, and Purification of Degradation-Resistant LfVk1_Ca Sequence

As described in (37-1), variant LfVk1_Ca (SEQ ID NO: 83) was constructed to have substitution of residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) in the hVk5-2 sequence for residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) in the hVk1 sequence (a human germline sequence). The variant was demonstrated to bind to calcium ion. Thus, it is possible to design C libraries containing LfVk1_Ca sequence. Meanwhile, there is no report on the properties of LfVk1_Ca sequence, and thus its feasibility was unknown. LfVk1_Ca sequence has Asp at positions 30, 31, and 32 (Kabat numbering). Thus, the Asp-Asp sequence which has been reported to be degraded under acidic condition is contained in the CDR1 sequence (J. Pharm. Biomed. Anal. (2008) 47(1), 23-30). It is desirable to avoid the degradation at acidic conditions from the viewpoint of the storage stability of antibody. Then, variants LfVk1_Ca1 (SEQ ID NO: 85), LfVk1_Ca2 (SEQ ID NO: 86), and LfVk1_Ca3 (SEQ ID NO: 87) were constructed to have substitution of Ala (A) residues for Asp (D) residues that are possibly sensitive to degradation. Amino acid substitution was carried out by a method known to those skilled in the art using the QuikChange Site-Directed Mutagenesis Kit (Stratagene). DNAs encoding the variants were inserted into animal expression vectors. In combination with an animal expression vector having an insert to express GC_H (SEQ ID NO: 55) as the heavy chain, the constructed animal expression vectors carrying DNA inserts for the variants were introduced into animal cells by the method described in Reference Example 33. The antibodies expressed in the animal cells introduced with the vectors were purified by the method described in Reference Example 33.

(37-4) Stability Assessment of Antibodies Having the Degradation-Resistant LfVk1_Ca Sequence

Whether the antibodies prepared as described in (37-3) were more resistant to degradation in solutions at pH 6.0 than the original antibodies having the LfVk1_Ca sequence provided for alteration was assessed by comparing the heterogeneity between respective antibodies after thermal acceleration. Each antibody was dialyzed against a solution of 20 mM Histidine-HCl, 150 mM NaCl (pH 6.0) under a condition of 4° C. overnight. Dialyzed antibodies were adjusted to 0.5 mg/mL and stored at 5° C. or 50° C. for three days. Each antibody after storage was subjected to ion-exchange chromatography using the method described in Reference Example 34. As shown in FIG. 58, the analysis result demonstrates that LfVk1_Ca1 with an alteration at degradation site was less heterogeneous and much more resistant to degradation from thermal acceleration than the original LfVk1_Ca sequence. Specifically, it was demonstrated that degradation occurred at the Asp (D) residue of position 30 in the LfVk1_Ca sequence but it could be prevented by amino acid alteration.

(37-5) Construction of a Light Chain LVk1_Ca Sequence Resistant to Degradation at the Asp Residue of Position 30, and Expression and Purification of Antibodies

The result described in (37-4) on the degradation resistance of the Ala-substituted form demonstrates that under acidic conditions the LfVk1_Ca sequence was degraded at the Asp (D) residue of position 30 (Kabat numbering) in its CDR sequence and the degradation could be prevented in the case of substitution of a different amino acid (in (37-4), an Ala (A) residue) for the Asp (D) residue at position 30 (Kabat numbering). Then, the present inventors tested whether even a sequence with a substitution of Ser (S), a main residue capable of chelating calcium ion, for the residue at position 30 (Kabat numbering) (referred to as LfVk1_Ca6; SEQ ID NO: 88) was resistant to degradation. Variants were prepared by the same method as described in Reference Example 29. The altered light chains LfVk1_Ca6 and LfVk1_Ca sequences were expressed in combination with a heavy chain GC_H (SEQ ID NO: 55). Antibodies were expressed and purified by the same method as described in Reference Example 36.

(37-6) Assessment of a Light Chain LVk1_Ca Sequence Resistant to Degradation at Asp Residue at Position 30

Purified antibodies prepared as described above were assessed for their storage stability under acidic conditions by the method described in (37-4). The result demonstrates that antibodies having the LfVk1_Ca6 sequence are more resistant to degradation than those having the original LfVk1_Ca sequence, as shown in FIG. 59.

Then, whether antibodies having the LfVk1_Ca sequence and antibodies having the LfVk1_Ca6 sequence bind to calcium ion was tested by the method described in Reference Example 33. The result is shown in Table 54. The Tm values of the Fab domains of antibodies having LfVk1_Ca sequence and antibodies having the degradation-resistant LfVk1_Ca6 sequence were shifted by 1° C. or more upon change in the calcium concentration in antibody solutions.

TABLE 54 CALCIUM ION LIGHT CHAIN CONCENTRATION ΔTm (° C.) VARIANT 3 μM 2 mM 2 mM-3 μM LfVk1_Ca 78.45 80.06 1.61 LfVk1_Ca6 78.44 79.74 1.30

Reference Example 38 Design of a Population of Antibody Molecules (Ca Library) with a Calcium Ion-Binding Motif Introduced into the Variable Region to Effectively Obtain Antibodies that Bind to Antigen in a Ca Concentration-Dependent Manner

Preferred calcium-binding motifs include, for example, the hVk5-2 sequence and its CDR sequence, as well as residues at positions 30, 31, 32, 50, and 92 (Kabat numbering) thereof. Other calcium binding motifs include the EF-hand motif possessed by calcium-binding proteins (e.g., calmodulin) and C-type lectin (e.g., ASGPR).

The Ca library consists of heavy and light chain variable regions. A human antibody sequence was used for the heavy chain variable region, and a calcium-binding motif was introduced into the light chain variable region. The hVk1 sequence was selected as a template sequence of the light chain variable region for introducing a calcium-binding motif. An antibody containing an LfVk1_Ca sequence obtained by introducing the CDR sequence of hVk5-2 (one of calcium-binding motifs) into the hVk1 sequence was shown to bind to calcium ions, as shown in Reference Example 36. Multiple amino acids were allowed to appear in the template sequence to diversify antigen-binding molecules that constitute the library. Positions exposed on the surface of a variable region which is likely to interact with the antigen were selected as those where multiple amino acids are allowed to appear. Specifically, positions 30, 31, 32, 34, 50, 53, 91, 92, 93, 94, and 96 (Kabat numbering) were selected as flexible residues.

The type and appearance frequency of amino acid residues that were subsequently allowed to appear were determined. The appearance frequency of amino acids in the flexible residues of the hVk1 and hVk3 sequences registered in the Kabat database (KABAT, E. A. ET AL.: ‘Sequences of proteins of immunological interest’, vol. 91, 1991. NIH PUBLICATION) was analyzed. Based on the analysis results, the type of amino acids that were allowed to appear in the Ca library were selected from those with higher appearance frequency at each position. At this time, amino acids whose appearance frequency was determined to be low based on the analysis results were also selected to avoid the bias of amino acid properties. The appearance frequency of the selected amino acids was determined in reference to the analysis results of the Kabat database.

A Ca library containing a calcium-binding motif with emphasis on the sequence diversity as to contain multiple amino acids at each residue other than the motif were designed as a Ca library in consideration of the amino acids and appearance frequency set as described above. The detailed designs of the Ca library are shown in Tables 9 and 10 (with the positions in each table representing the Kabat numbering). In addition, in Tables 9 and 10, if position 92 represented by the Kabat numbering is Asn (N), position 94 may be Leu (L) instead of Ser (S).

Reference Example 39 Ca Library Preparation

A gene library of antibody heavy-chain variable regions was amplified by PCR using a poly A RNA prepared from human PBMC, and commercial human poly A RNA, etc. as a template. As described in Reference Example 38, for the light chain variable regions of antibody, light chain variable regions of antibody that increase appearance frequency of antibodies which maintain a calcium-binding motif and can bind to an antigen in a calcium concentration-dependent manner were designed. In addition, for amino acid residues other than those with a calcium-binding motif introduced, a library of antibody light chain variable regions with evenly distributed amino acids of high appearance frequency in natural human antibodies as flexible residues was designed with reference to the information of amino acid appearance frequency in natural human antibodies (KABAT, E. A. ET AL.: ‘Sequences of proteins of immunological interest’, vol. 91, 1991, NIH PUBLICATION). A combination of the gene libraries of antibody heavy-chain and light-chain variable regions generated as described above, was inserted into a phagemid vector to construct a human antibody phage display library that presents Fab domains consisting of human antibody sequences (Methods Mol Biol. (2002) 178, 87-100).

The sequences of antibody genes isolated from E. coli introduced with an antibody gene library were determined according to the method described in Reference Example 43 below. The amino acid distribution in the sequences of isolated 290 clones and a designed amino acid distribution are shown in FIG. 60.

Reference Example 40 Examination of the Calcium Ion-Binding Activity of Molecules Contained in the Ca Library (40-1) Calcium Ion-Binding Activity of Molecules Contained in the Ca Library

As described in Reference Example 34, the hVk5-2 sequence that was demonstrated to bind to calcium ions is a sequence of low appearance frequency in the germline sequence. Thus, it was thought to be inefficient to obtain a calcium-binding antibody from an antibody library consisting of human germline sequences or from B cells obtained by immunizing a mouse expressing human antibodies. As a result, a Ca library was constructed. The presence or absence of a clone showing calcium binding in the constructed Ca library was examined.

(40-2) Expression and Purification of Antibodies

Clones contained in the Ca library were introduced into animal cell expression plasmids. Antibodies were expressed using the method described below. Cells of human fetal kidney cell-derived FreeStyle 293-F line (Invitrogen) were suspended in FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 1.33×10⁶ cells/ml (3 ml) to each well of a 6-well plate. The prepared plasmids were introduced into the cells by a lipofection method. The cells were cultured in a CO₂ incubator (37° C., 8%/CO₂, 90 rpm) for four days. By a method known to those skilled in the art, antibodies were purified using rProtein A Sepharose™ Fast Flow (Amersham Biosciences) from culture supernatants obtained as described above. The absorbance of solutions of purified antibodies was measured at 280 nm using a spectrophotometer. Antibody concentrations were calculated from the measured values by using the extinction coefficient determined by PACE method (Protein Science (1995) 4, 2411-2423).

(40-3) Assessment of Prepared Antibodies for their Calcium Ion Binding

Antibodies purified as described above were assessed for their calcium ion binding by the method described in Reference Example 26. The result is shown in Table 55. The Tm of the Fab domains of multiple antibodies contained in the Ca library changed depending on calcium ion concentration, suggesting that the library contains molecules that bind to calcium ion.

TABLE 55 SEQ ID NO CALCIUM ION HEAVY LIGHT CONCENTRATION ΔTm (° C.) ANTIBODY CHAIN CHAIN 3 μM 2 mM 2 mM-3 μM Ca_B01 89 100 70.88 71.45 0.57 Ca_E01 90 101 84.31 84.95 0.64 Ca_H01 91 102 77.87 79.49 1.62 Ca_D02 92 103 78.94 81.1 2.16 Ca_E02 93 104 81.41 83.18 1.77 Ca_H02 94 105 72.84 75.13 2.29 Ca_D03 95 106 87.39 86.78 −0.61 Ca_C01 96 107 74.74 74.92 0.18 Ca_G01 97 108 65.21 65.87 0.66 Ca_A03 98 109 80.64 81.89 1.25 Ca_B03 99 110 93.02 93.75 0.73

Reference Example 41 Isolation of Antibodies that Bind to IL-6 Receptor in a Ca-Dependent Manner

(41-1) Isolation of Antibody Fragments, which Bind to Antigens in a Ca-Dependent Manner, from Library by Bead Panning

The first selection from the constructed library of antibodies that bind in a Ca-dependent manner was performed by enriching only antibody fragments having the ability to bind to the antigen (IL-6 receptor).

Phages were produced by E. coli containing the constructed phagemids for phage display. To precipitate the phages, 2.5 M NaCl/10% PEG was added to the E. coli culture media of phage production. The precipitated phage population was diluted with TBS to prepare a phage library solution. Then, BSA and CaCl₂ were added to the phage library solution to adjust the final BSA concentration to 4% and the final calcium ion concentration to 1.2 mM. Regarding the panning method, the present inventors referred to general panning methods using antigens immobilized onto magnetic beads (J. Immunol. Methods. (2008) 332 (1-2), 2-9; J. Immunol. Methods. (2001) 247 (1-2), 191-203; Biotechnol. Prog. (2002) 18(2) 212-20; Mol. Cell Proteomics (2003) 2 (2), 61-9). The magnetic beads used were NeutrAvidin coated beads (Sera-Mag SpeedBeads NeutrAvidin-coated) or Streptavidin coated beads (Dynabeads M-280 Streptavidin).

Specifically, 250 μmol of biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library solution with the antigen at room temperature for 60 minutes. BSA-blocked magnetic beads were added and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed three times with 1 ml of 1.2 mM CaCl₂/TBST (TBST containing 1.2 mM CaCl₂) and then twice with 1 ml of 1.2 mM CaCl₂/TBS (TBST containing 1.2 mM CaCl₂). Then, the beads combined with 0.5 ml of 1 mg/ml trypsin were suspended at room temperature for 15 minutes, and immediately followed by separation of beads using a magnetic stand to collect a phage solution. The collected phage solution was added to 10 ml of E. coli strain ER2738 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was infected with the phages by culturing them while gently stirring at 37° C. for one hour. The infected E. coli was plated in a 225 mm×225 mm plate. Then, the phages were collected from the culture medium of the plated E. coli to prepare a phage library solution.

In the second-round panning, phages were enriched using the antigen-binding ability or the Ca-dependent binding ability as an indicator.

Specifically, when the enrichment was carried out using the antigen-binding ability as an indicator, 40 pmol of biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library solution with the antigen at room temperature for 60 minutes. BSA-blocked magnetic beads were added and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed three times with 1 ml of 1.2 mM CaCl₂/TBST and then twice with 1.2 mM CaCl₂/TBS. Then, the beads added with 0.5 ml of 1 mg/ml trypsin were suspended at room temperature for 15 minutes. Then immediately, the beads were separated using a magnetic stand to collect a phage solution. To eliminate the ability from phages displaying no Fab to infect E. coli, the pIII protein (helper phage-derived pill protein) of phages displaying no Fab was cleaved by adding 5 μl of 100 mg/ml trypsin to the collected phage solution. The recovered phage solution was added to 10 mL of the E. coli strain ER2738 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was cultured with gentle stirring at 37° C. for 1 hour to allow the phages to infect the E. coli. The infected E. coli was inoculated into a 225 mm×225 mm plate. Subsequently, the phages were recovered from the culture medium of the E. coli after inoculation to collect a phage library solution.

When the enrichment was carried out using the Ca-dependent binding ability as an indicator, 40 μmol of biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library solution with the antigen at room temperature for 60 minutes. BSA-blocked magnetic beads were added and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed with 1 ml of 1.2 mM CaCl₂/TBST and 1.2 mM CaCl₂/TBS. Then, the beads added with 0.1 ml of 2 mM EDTA/TBS (TBS containing 2 mM EDTA) were suspended at room temperature. Then immediately, the beads were separated using a magnetic stand to collect a phage solution. To eliminate the ability from phages displaying no Fab to infect E. coli, the pill protein (helper phage-derived pill protein) of phages displaying no Fab was cleaved by adding 5 μl of 100 mg/ml trypsin to the collected phage solution. The recovered phage solution was added to 10 mL of the E. coli strain ER2738 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was cultured with gentle stirring at 37° C. for 1 hour to allow the phages to infect the E. coli. The infected E. coli was inoculated into a 225 mm×225 mm plate. Subsequently, the phages were recovered from the culture medium of the E. coli after inoculation to collect a phage library solution.

(41-2) Examination by Phage ELISA

A phage-containing culture supernatant was collected according to a routine method (Methods Mol. Biol. (2002) 178, 133-145) from a single colony of E. coli, obtained as described above.

A culture supernatant containing phages, to which BSA and CaCl₂ were added was subjected to ELISA as described below. A StreptaWell 96 microtiter plate (Roche) was coated overnight with 100 μL of PBS containing the biotin-labeled antigen. Each well of said plate was washed with PBST to remove the antigen, and then the wells were blocked with 250 μL of 4% BSA-TBS for 1 hour or longer. Said plate with the prepared culture supernatant added to each well, from which the 4% BSA-TBS was removed, was allowed to stand undisturbed at 37° C. for 1 hour, allowing the binding of phage-presenting antibody to the antigen present in each well. To each well washed with 1.2 mM CaCl₂/TBST, 1.2 mM CaCl₂/TBS or 1 mM EDTA/TBS was added. The plate was allowed to stand undisturbed for 30 minutes at 37° C. for incubation. After washing with 1.2 mM CaCl₂/TBST, an HRP-conjugated anti-M13 antibody (Amersham Pharmacia Biotech) diluted with TBS at a concentration of 1.2 mM of ionized calcium concentration was added to each well, and the plate was incubated for 1 hour. After washing with 1.2 mM CaCl₂/TBST, the chromogenic reaction of the solution in each well with a TMB single solution (ZYMED) added was stopped by adding sulfuric acid. Subsequently, said developed color was measured by measuring absorbance at 450 nm.

The base sequences of genes amplified with specific primers were analyzed for the clones subjected to phage ELISA.

The result of phage ELISA and sequence analysis is shown in Table 56.

TABLE 56 LIBRARY Ca LIBRARY Ca LIBRARY DEPENDENT ANTIGEN- ANTIGEN- BINDING BINDING ENRICHMENT INDEX ABILITY ABILITY NUMBER OF PANNING 2 2 NUMBER OF EXAMINED 85 86 CLONES ELISA-POSITIVE 77 75 TYPES OF ELISA-POSITIVE 74 72 CLONE SEQUENCES TYPES OF Ca-DEPENDENT 13 47 BINDING CLONE SEQUENCES

(41-3) Expression and Purification of Antibodies

Clones that are determined to have Ca-dependent antigen binding ability as a result of phage ELISA were inserted into animal cell expression plasmids. Antibodies were expressed by the following method. Cells of human fetal kidney cell-derived FreeStyle 293-F (Invitrogen) were suspended in FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 1.33×10⁶ cells/ml (3 ml) into each well of a 6-well plate. The prepared plasmids were introduced into cells by a lipofection method. The cells were cultured for four days in a CO₂ incubator (37° C., 8% CO₂, 90 rpm). From the culture supernatants prepared as described above, antibodies were purified using the rProtein A Sepharose™ Fast Flow (Amersham Biosciences) by a method known to those skilled in the art. Absorbance at 280 nm of purified antibody solutions was measured using a spectrophotometer. Antibody concentrations were calculated from the determined values using an extinction coefficient calculated by the PACE method (Protein Science (1995) 4: 2411-2423).

(41-4) Assessment of Isolated Antibodies for their Ca-Dependent Binding Ability to Human IL-6 Receptor

Antibodies 6RC1IgG_010 (heavy chain SEQ ID NO: 133; light chain SEQ ID NO: 134), 6RCIIgG_012 (heavy chain SEQ ID NO: 135; light chain SEQ ID NO: 136), and 6RCIIgG_019 (heavy chain SEQ ID NO: 137; light chain SEQ ID NO: 138) isolated as described above were assessed for the Ca dependency of their human IL-6 receptor-binding activity by analyzing the interaction between the antibodies and human IL-6 receptor using Biacore T100 (GE Healthcare). Tocilizumab (heavy chain SEQ ID NO: 111; light chain SEQ ID NO: 112) was used as a control antibody that does not have Ca-dependent binding activity to human IL-6 receptor. The interaction was analyzed in solutions at 1.2 mM and 3 μM calcium ion concentration, corresponding to high and low calcium ion concentration conditions, respectively. An appropriate amount of Protein A/G (Invitrogen) was immobilized onto a Sensor chip CM5 (GE Healthcare) by an amine coupling method, and antibodies of interest were captured onto the chip. The two types of running buffers used were: 20 mM ACES/150 mM NaCl/0.05% (w/v) Tween20/1.2 mM CaCl₂ (pH 7.4); and 20 mM ACES/150 mM NaCl/0.05% (w/v) Tween20/3 μM CaCl₂ (pH 7.4). These buffers were each used to dilute human IL-6 receptor. All measurements were carried out at 37° C.

In the interaction analysis of the antigen-antibody reaction using antibody tocilizumab as a control antibody, and antibodies 6RCIIgG_010, 6RCIIgG_012, and 6RCIIgG_019, a diluted IL-6 receptor solution and a running buffer as a blank were injected at a flow rate of 5 μl/min for three minutes to allow IL-6 receptor to interact with antibodies tocilizumab, 6RCIIgG_010, 6RCIIgG_012, and 6RCIIgG_019 captured onto the sensor chip. Then, 10 mM glycine-HCl (pH 1.5) was injected at a flow rate of 30 μl/min for 30 seconds to regenerate the sensor chip.

Sensorgrams at the high calcium ion concentration obtained by the measurement using the above-described method are shown in FIG. 61.

Under the low calcium ion concentration condition, sensorgrams of antibodies tocilizumab, 6RCIIgG_010, 6RCIIgG_012, and 6RCIIgG_019 were also obtained by the same method. Sensorgrams at the low calcium ion concentration are shown in FIG. 62.

The result described above shows that the IL6 receptor-binding ability of antibodies 6RCIIgG_010, 6RCIIgG_012, and 6RCIIgG_019 was significantly reduced when the calcium ion concentration in the buffer was shifted from 1.2 mM to 3 μM.

Reference Example 42 Design of pH-Dependent Binding Antibody Library

(42-1) Method for Acquiring pH-Dependent Binding Antibodies

WO2009/125825 discloses a pH-dependent antigen-binding molecule whose properties are changed in neutral pH and acidic pH ranges by introducing a histidine into an antigen-binding molecule. The disclosed pH-dependent antigen-binding molecule is obtained by alteration to substitute a part of the amino acid sequence of the antigen-binding molecule of interest with a histidine. To obtain a pH-dependent antigen-binding molecule more efficiently without preliminarily obtaining the antigen-binding molecule of interest to be modified, one method may be obtaining an antigen-binding molecule that binds to a desired antigen from a population of antigen-binding molecules (referred to as His library) with a histidine introduced into the variable region (more preferably, a position potentially involved in antigen binding). It may be possible to efficiently obtain an antigen-binding molecule having desired properties from a His library, because histidine appears more frequently in antigen-binding molecules from His library than those from conventional antibody libraries.

(42-2) Design of a Population of Antibody Molecules (His Library) with Histidine Residue Introduced into their Variable Region to Effectively Acquire Antibodies that Bind to Antigen in a pH-Dependent Manner

First, positions for introducing a histidine were selected in a His library. WO 2009/125825 discloses generation of pH-dependent antigen-binding molecules by substituting amino acid residues in the sequences of IL-6 receptor antibodies, IL-6 antibodies, and IL-31 receptor antibodies with a histidine. In addition, an egg white lysozyme antibody (FEBS Letter 11483, 309, 1, 85-88) and hepcidin antibody (WO2009/139822) having a pH-dependent antigen-binding ability were generated by substituting the amino acid sequence of the antigen-binding molecule with histidines. Positions where histidines were introduced in the IL-6 receptor antibody, IL-6 antibody, IL-31 receptor antibody, egg white lysozyme antibody, and hepcidin antibody are shown in Table 57. Positions shown in Table 57 may be listed as candidate positions that can control the antigen-antibody binding. In addition, besides the positions shown in Table 57, positions that are likely to have contact with antigen were also considered to be suitable for introduction of histidines.

TABLE 57 ANTIBODY CHAIN POSITION (Kabat) IL-6 RECEPTOR H 27 31 32 35 50 58 62 100B 102 ANTIBODY L 28 31 32 53 56 92 IL-6 ANTIBODY H 32 59 61 99 L 53 54 90 94 IL-31 RECEPTOR H 33 ANTIBODY L EGG-WHILE LYSOZYME H 33 98 ANTIBODY L 54 HEPCIDIN ANTIBODY H 52 57 99 107 L 27 89

In the His library consisting of heavy-chain and light-chain variable regions, a human antibody sequence was used for the heavy chain variable region, and histidines were introduced into the light chain variable region. The positions listed above and positions that may be involved in antigen binding, i.e., positions 30, 32, 50, 53, 91, 92, and 93 (Kabat numbering, Kabat E A et al. 1991. Sequence of Proteins of Immunological Interest. NIH) in the light chain were selected as positions for introducing histidines in the His library. In addition, the hVk1 sequence was selected as a template sequence of the light chain variable region for introducing histidines. Multiple amino acids were allowed to appear in the template sequence to diversify antigen-binding molecules that constitute the library. Positions exposed on the surface of a variable region that is likely to interact with the antigen were selected as those where multiple amino acids are allowed to appear. Specifically, positions 30, 31, 32, 34, 50, 53, 91, 92, 93, 94, and 96 of the light chain (Kabat numbering, Kabat E A et al. 1991. Sequence of Proteins of Immunological Interest. NIH) were selected as flexible residues.

The type and appearance frequency of amino acid residues that were subsequently allowed to appear were determined. The appearance frequency of amino acids in the flexible residues in the hVk1 and hVk3 sequences registered in the Kabat database (KABAT. E. A. ET AL.: ‘Sequences of proteins of immunological interest’, vol. 91, 1991, NIH PUBLICATION) was analyzed. Based on the analysis results, the type of amino acids that were allowed to appear in the His library were selected from those with higher appearance frequency at each position. At this time, amino acids whose appearance frequency was determined to be low based on the analysis results were also selected to avoid the bias of amino acid properties. The appearance frequency of the selected amino acids was determined in reference to the analysis results of the Kabat database.

As His libraries, His library 1 which is fixed to necessarily incorporate a single histidine into each CDR, and His library 2 which is more emphasized on sequence diversity than the His library 1 were designed by taking the amino acids and appearance frequency set as described above into consideration. The detailed designs of His libraries 1 and 2 are shown in Tables 7 and 8 (with the positions in each table representing the Kabat numbering). In Tables 7 and 8, Ser (S) at position 94 can be excluded if position 92 represented by the Kabat numbering is Asn (N).

Reference Example 43 Preparation of a Phage Display Library for Human Antibodies (His Library 1) to Obtain an Antibody that Binds to Antigen in a pH-Dependent Manner

A gene library of antibody heavy-chain variable regions was amplified by PCR using a poly A RNA prepared from human PBMC, and commercial human poly A RNA as a template. A gene library of antibody light-chain variable regions designed as His library 1 as described in Reference Example 42 was amplified using PCR. A combination of the gene libraries of antibody heavy-chain and light-chain variable regions generated as described above was inserted into a phagemid vector to construct a human antibody phage display library which presents Fab domains consisting of human antibody sequences. For the construction method, Methods Mol Biol. (2002) 178, 87-100 was used as a reference. For the construction of the library, the sequences of a phage display library with a trypsin cleavage sequence inserted into a linker region connecting the phagemid Fab to the phage pill protein, and between the N2 and CT domains of the helper phage pIII protein gene were used. Sequences of the antibody genes isolated from E. coli into which the antibody gene library was introduced were identified, and sequence information was obtained for 132 clones. The designed amino acid distribution and the amino acid distribution of the identified sequences are shown in FIG. 63. A library containing various sequences corresponding to the designed amino acid distribution was constructed.

Reference Example 44 Isolation of Antibodies that Bind to IL-6R in a pH-Dependent Manner

(44-1) Isolation of Antibody Fragments, which Bind to Antigens in a pH-Dependent Manner, from the Library by Bead Panning

The first selection from the constructed His library 1 was performed by enriching only antibody fragments with antigen (IL-6R) binding ability.

Phages were produced by E. coli containing the constructed phagemids for phage display. To precipitate the phages, 2.5 M NaCl/10% PEG was added to the E. coli culture media of phage production. The precipitated phage population was diluted with TBS to prepare a phage library solution. BSA and CaCl₂ were added to the phage library solution to adjust the final BSA concentration to 4% and the final calcium ion concentration to 1.2 mM. Regarding the panning method, the present inventors referred to general panning methods using antigens immobilized onto magnetic beads (J. Immunol. Methods. (2008) 332 (1-2), 2-9; J. Immunol. Methods. (2001) 247 (1-2), 191-203; Biotechnol. Prog. (2002) 18(2) 212-20. Mol. Cell Proteomics (2003) 2 (2), 61-9). The magnetic beads used were NeutrAvidin coated beads (Sera-Mag SpeedBeads NeutrAvidin-coated) or Streptavidin coated beads (Dynabeads M-280 Streptavidin).

Specifically, 250 μmol of biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library solution with the antigen at room temperature for 60 minutes. BSA-blocked magnetic beads were added and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed three times with 1 ml of 1.2 mM CaCl₂/TBST (TBS containing 1.2 mM CaCl₂ and 0.1% Tween20) and then twice with 1 ml of 1.2 mM CaCl₂/TBS (pH 7.6). Then, the beads added with 0.5 ml of 1 mg/ml trypsin were suspended at room temperature for 15 minutes, and then immediately separated using a magnetic stand to collect a phage solution. The collected phage solution was added to 10 ml of E. coli strain ER2738 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was infected with the phages by culturing them while gently stirring at 37° C. for one hour. The infected E. coli was plated in a 225 mm×225 mm plate. Then, the phages were collected from the culture medium of the plated E. coli to prepare a phage library solution.

To enrich the phages, the second and subsequent rounds of panning were performed using the antigen-binding ability or the pH-dependent binding ability as an indicator. Specifically, 40 μmol of the biotin-labeled antigen was added to the prepared phage library solution to allow the contact of the phage library solution with the antigen at room temperature for 60 minutes. BSA-blocked magnetic beads were added and allowed to bind to antigen/phage complexes at room temperature for 15 minutes. The beads were washed multiple times with 1 ml of 1.2 mM CaCl₂/TBST and 1.2 mM CaCl₂/TBS. Then, when the phages were enriched using the antigen-binding ability as an indicator, the beads added with 0.5 ml of 1 mg/ml trypsin were suspended at room temperature for 15 minutes, and then immediately separated using a magnetic stand to collect a phage solution. Alternatively, when the phages were enriched using the pH-dependent antigen-binding ability as an indicator, the beads added with 0.1 ml of 50 mM MES/1.2 mM CaCl₂/150 mM NaCl (pH 5.5) were suspended at room temperature, and then immediately separated using a magnetic stand to collect a phage solution. To eliminate the ability from phages displaying no Fab to infect E. coli, the pIII protein (helper phage-derived pIII protein) of phages displaying no Fab was cleaved by adding 5 μl of 100 mg/ml trypsin to the collected phage solution. The collected phages were added to 10 ml of E. coli strain ER2738 in a logarithmic growth phase (OD600 of 0.4-0.7). The E. coli was infected with the phages by culturing them while gently stirring at 37° C. for one hour. The infected E. coli was plated in a 225 mm×225 mm plate. Then, the phages were collected from the culture medium of the plated E. coli to collect a phage library solution. The panning using the antigen-binding ability or the pH-dependent binding ability as an indicator was repeated twice.

(44-2) Assessment by Phage ELISA

Phage-containing culture supernatants were collected according to a conventional method (Methods Mol. Biol. (2002) 178, 133-145) from single colonies of E. coli obtained by the method described above.

To the phage-containing culture supernatants, BSA and CaCl₂ were added at a final concentration of 4% BSA and at a final calcium ion concentration of 1.2 mM. These phage-containing culture supernatants were subjected to ELISA by the following procedure. A StreptaWell 96 microtiter plate (Roche) was coated overnight with 100 μl of PBS containing the biotin-labeled antigen. After washing each well of the plate with PBST (PBS containing 0.1% Tween20) to remove the antigen, the wells were blocked with 250 μl of 4% BSA/TBS for one hour or more. After removing 4% BSA/TBS, the prepared culture supernatants were added to each well. The antibodies presented on the phages were allowed to bind to the antigens on each well by incubating the plate at 37° C. for one hour. Following wash with 1.2 mM CaCl₂/TBST, 1.2 mM CaCl₂/TBS (pH 7.6) or 1.2 mM CaCl₂/TBS (pH 5.5) was added to each well. The plate was incubated at 37° C. for 30 minutes. After washing with 1.2 mM CaCl₂/TBST, HRP-coupled anti-M13 antibody (Amersham Pharmacia Biotech) diluted with TBS containing 4% BSA and 1.2 mM ionized calcium was added to each well. The plate was incubated for one hour. After washing with 1.2 mM CaCl₂/TBST, TMB single solution (ZYMED) was added to each well. The chromogenic reaction in the solution of each well was stopped by adding sulfuric acid, and then the absorbance at 450 nm was measured to assess the color development.

When enrichment was carried out using the antigen-binding ability as an indicator, phage ELISA following two rounds of panning showed that 17 of 96 clones were ELISA positive in an antigen-specific manner. Thus, clones were analyzed after three rounds of panning. Meanwhile, when enrichment was carried out using the pH-dependent antigen-binding ability as an indicator, phage ELISA following two rounds of panning showed that 70 of 94 clones were positive in ELISA. Thus, clones were analyzed after two rounds of panning.

The base sequences of genes amplified with specific primers were analyzed for the clones subjected to phage ELISA. The results of phage ELISA and sequence analysis are shown in Table 58 below.

TABLE 58 LIBRARY His LIBRARY 1 His LIBRARY 1 pH-DEPENDENT ANTIGEN- ANTIGEN- BINDING BINDING ENRICHMENT INDEX ABILITY ABILITY NUMBER OF PANNING 3 2 NUMBER OF EXAMINED 80 94 CLONES ELISA-POSITIVE 76 70 TYPES OF ELISA-POSITIVE 30 67 CLONE SEQUENCES TYPES OF pH-DEPENDENT 22 47 BINDING CLONE SEQUENCES

By the same method, antibodies with pH-dependent antigen-binding ability were isolated from the naive human antibody phage display library. When enrichment was carried out using the antigen-binding ability as an indicator, 13 types of pH-dependent binding antibodies were isolated from 88 clones tested. Meanwhile, when enrichment was carried out using the pH-dependent antigen-binding ability as an indicator, 27 types of pH-dependent binding antibodies were isolated from 83 clones tested.

The result described above demonstrated that the variation of clones with pH-dependent antigen-binding ability isolated from the His library 1 was larger as compared to the naive human antibody phage display library.

(44-3) Expression and Purification of Antibodies

Clones assumed to have pH-dependent antigen-binding ability based on the result of phage ELISA were introduced into animal cell expression plasmids. Antibodies were expressed using the method described below. Cells of human fetal kidney cell-derived FreeStyle 293-F line (Invitrogen) were suspended in FreeStyle 293 Expression Medium (Invitrogen), and plated at a cell density of 1.33×10⁶ cells/ml (3 ml) to each well of a 6-well plate. The prepared plasmids were introduced into the cells by a lipofection method. The cells were cultured in a CO₂ incubator (37° C., 8% CO₂, 90 rpm) for four days. By a method known to those skilled in the art, antibodies were purified using rProtein A Sepharose™ Fast Flow (Amersham Biosciences) from culture supernatants obtained as described above. The absorbance of solutions of purified antibodies was measured at 280 nm using a spectrophotometer. Antibody concentrations were calculated from the measured values by using the extinction coefficient determined by PACE method (Protein Science (1995) 4, 2411-2423).

(44-4) Assessment of Isolated Antibodies for their pH-Dependent Binding Ability to Human IL-6 Receptor

Antibodies 6RpH#01 (heavy chain SEQ ID NO: 139; light chain SEQ ID NO: 140), 6RpH#02 (heavy chain SEQ ID NO: 141; light chain SEQ ID NO: 142), and 6RpH#03 (heavy chain SEQ ID NO: 143; light chain SEQ ID NO: 144) isolated as described in (44-3) were assessed for the pH dependency of their human IL-6 receptor-binding activity by analyzing the interaction between the antibodies and human IL-6 receptor using Biacore T100 (GE Healthcare). Tocilizumab (heavy chain SEQ ID NO: 111; light chain SEQ ID NO: 112) was used as a control antibody that does not have pH-dependent binding activity to human IL-6 receptor. The interaction for the antigen-antibody reaction was analyzed in solutions at pH 7.4 and pH 6.0, corresponding to a neutral pH and acidic pH conditions, respectively. An appropriate amount of Protein A/G (Invitrogen) was immobilized onto a Sensor chip CM5 (GE Healthcare) by an amine coupling method, and about 300 RU each of antibodies of interest were captured onto the chip. The two types of running buffers used were: 20 mM ACES/150 mM NaCl/0.05% (w/v) Tween20/1.2 mM CaCl₂ (pH 7.4); and 20 mM ACES/150 mM NaCl/0.05% (w/v) Tween20/1.2 mM CaCl₂ (pH 6.0). These buffers were each used to dilute human IL-6 receptor. All measurements were carried out at 37° C.

In the interaction analysis of the antigen-antibody reaction using tocilizumab as a control antibody, and antibodies 6RpH#01, 6RpH#02, and 6RpH#03, a diluted IL-6 receptor solution and a running buffer as a blank were injected at a flow rate of 5 μl/min for three minutes to allow IL-6 receptor to interact with antibodies tocilizumab, 6RpH#01, 6RpH#02, and 6RpH#03 captured onto the sensor chip. Then, 10 mM glycine-HCl (pH 1.5) was injected at a flow rate of 30 μl/min for 30 seconds to regenerate the sensor chip.

Sensorgrams at pH 7.4 obtained by the measurement using the method described above are shown in FIG. 64. Sensorgrams under the condition of pH 6.0 obtained by the same method are shown in FIG. 65.

The result described above shows that the IL-6 receptor-binding ability of antibodies 6RpH#01, 6RpH#02, and 6RpH#03 was significantly reduced when the buffer pH was shifted from pH 7.4 to pH 6.0.

INDUSTRIAL APPLICABILITY

The present invention has successfully obtained antigen-binding molecules that promote antigen elimination from blood (from serum or plasma), wherein the physiological activities of an antigen having two or more physiological activities which are difficult to inhibit in vitro with a single type of antigen-binding molecule can be reduced with a single type of antigen-binding molecule in vivo. Diseases that are caused by an antigen with multiple physiological activities have been difficult to treat with a single type of pharmaceutical agent alone. The present invention can provide effective pharmaceutical agents for such diseases. 

1-53. (canceled)
 54. A method of treatment comprising identifying a patient in need of treatment for a condition that is treatable by reducing the level of an antigen in blood, wherein the antigen has two or more physiological activities; administering to the patient a therapeutically effective amount of an antibody that has an antigen-binding domain as described in (a) below and an Fc region as described in (b) below: (a) the antigen-binding domain binds to the antigen and thereby inhibits a first physiological activity of the antigen but not a second physiological activity of the antigen, wherein the antigen-binding domain's antigen-binding activity varies with pH as described in (i) below, or with calcium ion concentration as described in (ii) below, or with both: (i) the antigen-binding activity is lower at a first pH in the range of 4.0 to 6.5 than at a second pH in the range of 7.0 to 9.0, wherein the ratio of (A) the KD value for antigen binding by the selected antigen-binding domain at the first pH, to (B) the KD value for antigen binding by the selected antigen-binding domain at the second pH (KD (first pH)/KD (second pH)) is 2 or more, (ii) the antigen-binding activity is lower at a first calcium ion concentration in the range of 0.1 uM to 30 uM than at a second calcium ion concentration in the range of 100 uM to 10 mM, wherein the ratio of (A) the KD value for antigen binding by the selected antigen-binding domain at the first calcium ion concentration, to (B) the KD value for antigen binding by the selected antigen-binding domain at the second calcium ion concentration (KD (first calcium ion concentration)/KD (second calcium ion concentration)) is 2 or more; and (b) the Fc region: (1) has an amino acid sequence that is not identical to the sequence of an Fc region of any native human IgG, (2) binds a neonatal Fc Receptor (FcRn) at a pH in the range of 4.0 to 6.5, and (3) at a pH in the range of 7.0 to 9.0, binds to a human Fc receptor with affinity greater than the affinity with which any native human IgG binds to the human Fc receptor.
 55. The method of claim 54, wherein the first physiological activity of the antigen is mediated by the antigen's binding to a first target molecule; the second physiological activity of the antigen is mediated by the antigen's binding to a second target molecule that is different from the first target molecule; and the antibody inhibits binding of the antigen to the first target molecule but not to the second target molecule.
 56. The method of claim 54, wherein the human Fc receptor is human FcRn or human Fcγ receptor.
 57. The method of claim 54, wherein administration of the antibody to the patient reduces the concentration of the antigen in plasma of the patient.
 58. The method of claim 54, wherein the antigen-binding domain of the antibody comprises at least one histidine residue.
 59. The method of claim 56, wherein the human Fc receptor is human FcRn, and wherein the Fc region of the antibody differs from a naturally occurring Fc region of a native human IgG at one or more positions selected from the following positions (all positions by EU numbering): 234, 235, 236, 237, 238, 239, 244, 245, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 260, 262, 265, 267, 270, 272, 274, 279, 280, 282, 283, 284, 285, 286, 288, 289, 293, 295, 297, 298, 303, 305, 307, 308, 309, 311, 312, 313, 314, 315, 316, 317, 318, 325, 326, 327, 328, 329, 330, 332, 334, 338, 339, 340, 341, 343, 345, 360, 361, 362, 375, 376, 377, 378, 380, 382, 384, 385, 386, 387, 389, 390, 391, 413, 422, 423, 424, 427, 428, 430, 431, 433, 434, 435, 436, 437, 438, 440, and
 442. 60. The method of claim 59, wherein the one or more positions include at least one from the following positions (all positions by EU numbering), substituted with the indicated amino acid: the amino acid at position 234 is Arg; the amino acid at position 235 is Gly, Lys, or Arg; the amino acid at position 236 is Ala, Asp, Lys, or Arg; the amino acid at position 237 is Lys, Met, or Arg; the amino acid at position 238 is Ala, Asp, Lys, Leu, or Arg; the amino acid at position 239 is Asp or Lys; the amino acid at position 244 is Leu; the amino acid at position 245 is Arg; the amino acid at position 248 is Ile or Tyr; the amino acid at position 249 is Pro; the amino acid at position 250 is Ala, Glu, Phe, Ile, Met, Gln, Ser, Val, Trp, Gly, His, Leu, Asn, or Tyr; the amino acid at position 251 is Arg, Asp, Glu, or Leu; the amino acid at position 252 is Phe, Ser, Thr, Trp, or Tyr; the amino acid at position 253 is Val; the amino acid at position 254 is Ala, Gly, His, Ile, Gln, Ser, Val, or Thr; the amino acid at position 255 is Ala, Asp, Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Gly, Ser, Trp, Tyr, or Glu; the amino acid at position 256 is Ala, Asp, Glu, Arg, Asn, Pro, Thr, Ser, or Gln; the amino acid at position 257 is Ala, Gly, Ile, Leu, Met, Asn, Ser, Thr, or Val; the amino acid at position 258 is Asp or His; the amino acid at position 260 is Ser; the amino acid at position 262 is Leu; the amino acid at position 265 is Ala; the amino acid at position 267 is Met or Leu; the amino acid at position 270 is Lys or Phe; the amino acid at position 272 is Ala, Leu, or Arg; the amino acid at position 274 is Ala; the amino acid at position 279 is Leu, Ala, Asp, Gly, His, Met, Asn, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 280 is Ala, Gly, His, Lys, Asn, Gln, Arg, Ser, Thr, or Glu; the amino acid at position 282 is Ala or Asp; the amino acid at position 283 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 284 is Lys; the amino acid at position 285 is Asn; the amino acid at position 286 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or Glu; the amino acid at position 288 is Ala, Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Gln, Arg, Val, Trp, Tyr, or Ser; the amino acid at position 289 is His; the amino acid at position 293 is Val; the amino acid at position 295 is Met; the amino acid at position 297 is Ala; the amino acid at position 298 is Gly; the amino acid at position 303 is Ala; the amino acid at position 305 is Ala or Thr; the amino acid at position 307 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 308 is Ala, Phe, Ile, Leu, Met, Pro, Gln, or Thr; the amino acid at position 309 is Ala, Asp, Glu, Pro, His, or Arg; the amino acid at position 311 is Ala, His, Glu, Lys, Leu, Met, Ser, Val, Trp, or Ile; the amino acid at position 312 is Ala, Asp, Pro, or His; the amino acid at position 313 is Tyr or Phe; the amino acid at position 314 is Ala, Leu, Lys, or Arg; the amino acid at position 315 is Ala, Asp, Glu, Phe, Gly, Ile, Lys, Leu, Met, Gln, Arg, Ser, Thr, Val, Trp, Tyr, or His; the amino acid at position 316 is Ala, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Asp; the amino acid at position 317 is Ala or Pro; the amino acid at position 318 is Asn or Thr; the amino acid at position 325 is Ala, Gly, Met, Leu, Ile, or Ser; the amino acid at position 326 is Asp; the amino acid at position 327 is Gly; the amino acid at position 328 is Arg, Asp, Glu, or Tyr; the amino acid at position 329 is Lys or Arg; the amino acid at position 330 is Leu; the amino acid at position 332 is Glu, Phe, His, Lys, Leu, Met, Arg, Ser, Trp, or Val; the amino acid at position 334 is Leu; the amino acid at position 338 is Ala; the amino acid at position 339 is Asn, Thr, or Trp; the amino acid at position 340 is Ala; the amino acid at position 341 is Pro; the amino acid at position 343 is Glu, His, Lys, Gln, Arg, Thr, or Tyr; the amino acid at position 345 is Ala; the amino acid at position 360 is His; the amino acid at position 361 is Ala; the amino acid at position 362 is Ala; the amino acid at position 375 is Ala or Arg; the amino acid at position 376 is Ala, Gly, Ile, Met, Pro, Thr, or Val; the amino acid at position 377 is Lys; the amino acid at position 378 is Asp, Asn, or Val; the amino acid at position 380 is Ala, Asn, Thr, or Ser; the amino acid at position 382 is Ala, Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Trp, Tyr, or Val; the amino acid at position 384 is Ala; the amino acid at position 385 is Ala, Gly, Lys, Ser, Thr, Asp, His, or Arg; the amino acid at position 386 is Arg, Asp, Ile, Met, Ser, Thr, Lys, or Pro; the amino acid at position 387 is Ala, Arg, His, Pro, Ser, Thr, or Glu; the amino acid at position 389 is Ala, Asn, Pro, or Ser; the amino acid at position 390 is Ala; the amino acid at position 391 is Ala; the amino acid at position 413 is Ala; the amino acid at position 423 is Asn; the amino acid at position 424 is Ala or Glu; the amino acid at position 427 is Asn; the amino acid at position 428 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 430 is Ala, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 431 is His or Asn; the amino acid at position 433 is Arg, Gln, His, Ile, Pro, Ser, or Lys; the amino acid at position 434 is Ala, Phe, Gly, Met, His, Ser, Trp, or Tyr; the amino acid at position 435 is Lys, Arg, or Asn; the amino acid at position 436 is Ala, His, Ile, Leu, Glu, Phe, Gly, Lys, Met, Asn, Arg, Ser, Thr, Trp, or Val; the amino acid at position 437 is Arg; the amino acid at position 438 is Lys, Leu, Thr, or Trp; the amino acid at position 440 is Lys; and the amino acid at position 442 is Lys.
 61. The method claim of 56, wherein the human Fc receptor is human Fcγ receptor, and wherein the one or more positions are selected from the following positions (all positions by EU numbering): 221, 222, 223, 224, 225, 227, 228, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 243, 244, 245, 246, 247, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 278, 279, 280, 281, 282, 283, 284, 285, 286, 288, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 307, 308, 309, 311, 312, 313, 314, 315, 316, 317, 318, 320, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 339, 341, 343, 375, 376, 377, 378, 379, 380, 382, 385, 386, 387, 389, 392, 396, 421, 423, 427, 428, 429, 430, 431, 433, 434, 436, 438, 440, and
 442. 62. The method claim of 61, wherein the one or more positions include at least one of the following positions (all positions by EU numbering), substituted with the indicated amino acid: the amino acid at position 221 is Lys or Tyr; the amino acid at position 222 is Phe, Trp, Glu, or Tyr; the amino acid at position 223 is Phe, Trp, Glu, or Lys; the amino acid at position 224 is Phe, Trp, Glu, or Tyr; the amino acid at position 225 is Glu, Lys, or Trp; the amino acid at position 227 is Glu, Gly, Lys, or Tyr; the amino acid at position 228 is Glu, Gly, Lys, or Tyr; the amino acid at position 230 is Ala, Glu, Gly, or Tyr; the amino acid at position 231 is Glu, Gly, Lys, Pro, or Tyr; the amino acid at position 232 is Glu, Gly, Lys, or Tyr; the amino acid at position 233 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 234 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 235 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 236 is Ala, Asp, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 237 is Ala, Asp, Glu, Phe, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 238 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 239 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 240 is Ala, Ile, Met, or Thr; the amino acid at position 241 is Asp, Glu, Leu, Arg, Trp, or Tyr; the amino acid at position 243 is Leu, Glu, Leu, Gln, Arg, Trp, or Tyr; the amino acid at position 244 is His; the amino acid at position 245 is Ala; the amino acid at position 246 is Asp, Glu, His, or Tyr; the amino acid at position 247 is Ala, Phe, Gly, His, Ile, Leu, Met, Thr, Val, or Tyr; the amino acid at position 249 is Glu, His, Gln, or Tyr; the amino acid at position 250 is Glu or Gln; the amino acid at position 251 is Phe; the amino acid at position 254 is Phe, Met, or Tyr; the amino acid at position 255 is Glu, Leu, or Tyr; the amino acid at position 256 is Ala, Met, or Pro; the amino acid at position 258 is Asp, Glu, His, Ser, or Tyr; the amino acid at position 260 is Asp, Glu, His, or Tyr; the amino acid at position 262 is Ala, Glu, Phe, Ile, or Thr; the amino acid at position 263 is Ala, Ile, Met, or Thr; the amino acid at position 264 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 265 is Ala, Glu, Leu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 266 is Ala, Phe, Ile, Leu, Met, or Thr; the amino acid at position 267 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 268 is Ala, Asp, Glu, Phe, Gly, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr, Val, or Trp; the amino acid at position 269 is Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 270 is Glu, Phe, Gly, His, Ile, Leu, Met, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 271 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 272 is Asp, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 273 is Phe or Ile; the amino acid at position 274 is Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 275 is Leu or Trp; the amino acid at position 276 is Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 278 is Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp; the amino acid at position 279 is Ala; the amino acid at position 280 is Ala, Gly, His, Lys, Leu, Pro, Gln, Trp, or Tyr; the amino acid at position 281 is Asp, Lys, Pro, or Tyr; the amino acid at position 282 is Glu, Gly, Lys, Pro, or Tyr; the amino acid at position 283 is Ala, Gly, His, Ile, Lys, Leu, Met, Pro, Arg, or Tyr; the amino acid at position 284 is Asp, Glu, Leu, Asn, Thr, or Tyr; the amino acid at position 285 is Asp, Glu, Lys, Gln, Trp, or Tyr; the amino acid at position 286 is Glu, Gly, Pro, or Tyr; the amino acid at position 288 is Asn, Asp, Glu, or Tyr; the amino acid at position 290 is Asp, Gly, His, Leu, Asn, Ser, Thr, Trp, or Tyr; the amino acid at position 291 is Asp, Glu, Gly, His, Ile, Gln, or Thr; the amino acid at position 292 is Ala, Asp, Glu, Pro, Thr, or Tyr; the amino acid at position 293 is Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 294 is Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 295 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 296 is Ala, Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, or Val; the amino acid at position 297 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 298 is Ala, Asp, Glu, Phe, His, Ile, Lys, Met, Asn, Gln, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 299 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 300 is Ala, Asp, Glu, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, or Trp; the amino acid at position 301 is Asp, Glu, His, or Tyr; the amino acid at position 302 is Ile; the amino acid at position 303 is Asp, Gly, or Tyr; the amino acid at position 304 is Asp, His, Leu, Asn, or Thr; the amino acid at position 305 is Glu, Ile, Thr, or Tyr; the amino acid at position 311 is Ala, Asp, Asn, Thr, Val or Tyr; the amino acid at position 313 is Phe; the amino acid at position 315 is Leu; the amino acid at position 317 is Glu or Gln; the amino acid at position 318 is His, Leu, Asn, Pro, Gln, Arg, Thr, Val, or Tyr; the amino acid at position 320 is Asp, Phe, Gly, His, Ile, Leu, Asn, Pro, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 322 is Ala, Asp, Phe, Gly, His, Ile, Pro, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 323 is Ile, Leu, or Met; the amino acid at position 324 is Asp, Phe, Gly, His, Ile, Leu, Met, Pro, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 325 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 326 is Ala, Asp, Glu, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Gln, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 327 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Thr, Val, Trp, or Tyr; the amino acid at position 328 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 329 is Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 330 is Cys, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 331 is Asp, Phe, His, Ile, Leu, Met, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 332 is Ala, Asp, Glu, Phe, Gly, His, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 333 is Ala, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Pro, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 334 is Ala, Glu, Phe, His, Ile, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 335 is Asp, Phe, Gly, His, Ile, Leu, Met, Asn, Pro, Arg, Ser, Val, Trp, or Tyr; the amino acid at position 336 is Glu, Lys, or Tyr; the amino acid at position 337 is Asp, Glu, His, or Asn; the amino acid at position 339 is Asp, Phe, Gly, Ile, Lys, Met, Asn, Gln, Arg, Ser, or Thr; the amino acid at position 376 is Ala or Val; the amino acid at position 377 is Gly or Lys; the amino acid at position 378 is Asp; the amino acid at position 379 is Asn; the amino acid at position 380 is Ala, Asn, or Ser; the amino acid at position 382 is Ala or Ile; the amino acid at position 385 is Glu; the amino acid at position 392 is Thr; the amino acid at position 396 is Asp, Glu, Phe, Ile, Lys, Leu, Met, Gln, Arg, or Tyr; the amino acid at position 421 is Lys; the amino acid at position 427 is Asn; the amino acid at position 428 is Phe or Leu; the amino acid at position 429 is Met; the amino acid at position 434 is Trp; the amino acid at position 436 is Ile; the amino acid at position 440 is Gly, His, Ile, Leu, or Tyr.
 63. The method of claim 56, wherein the human Fc receptor is a human Fcγ receptor selected from FcγRIa, FcγRIIa, FcγRIIb, and FcγRIIIa.
 64. The method of claim 61, wherein the one or more positions include position 238 substituted with Asp and position 271 substituted with Gly (all positions by EU numbering).
 65. The method of claim 64, wherein the one or more positions also include at least one position from the following group of positions (all positions by EU numbering): 233, 234, 237, 244, 245, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262, 264, 265, 266, 267, 268, 269, 270, 272, 279, 283, 285, 286, 288, 293, 296, 307, 308, 309, 311, 312, 314, 316, 317, 318, 326, 327, 330, 331, 332, 333, 339, 341, 343, 375, 376, 377, 378, 380, 382, 385, 386, 387, 389, 396, 423, 427, 428, 430, 431, 433, 434, 436, 438, 440, and
 442. 66. The method of 65, wherein at least one position from the following positions (all positions by EU numbering) is substituted with the indicated amino acid: the amino acid at position 233 is Asp; the amino acid at position 234 is Tyr; the amino acid at position 237 is Asp; the amino acid at position 264 is Ile; the amino acid at position 265 is Glu; the amino acid at position 266 is Phe, Met, or Leu; the amino acid at position 267 is Ala, Glu, Gly, or Gln; the amino acid at position 268 is Asp or Glu; the amino acid at position 269 is Asp; the amino acid at position 272 is Asp, Phe, Ile, Met, Asn, or Gln; the amino acid at position 296 is Asp; the amino acid at position 326 is Ala or Asp; the amino acid at position 327 is Gly; the amino acid at position 330 is Lys or Arg; the amino acid at position 331 is Ser; the amino acid at position 332 is Thr; the amino acid at position 333 is Thr, Lys, or Arg; the amino acid at position 396 is Asp, Glu, Phe, Ile, Lys, Leu, Met, Gln, Arg, or Tyr.
 67. The method of claim 64, wherein the one or more positions also include at least one from the following group of positions (all positions by EU numbering): 244, 245, 249, 250, 251, 252, 254, 255, 256, 257, 258, 260, 262, 270, 272, 279, 283, 285, 286, 288, 293, 307, 308, 309, 311, 312, 314, 316, 317, 318, 332, 339, 341, 343, 375, 376, 377, 378, 380, 382, 385, 386, 387, 389, 423, 427, 428, 430, 431, 433, 434, 436, 438, 440, and
 442. 68. The method of claim 67, wherein at least one position from the following positions (all positions by EU numbering) is substituted with the indicated amino acid: the amino acid at position 244 is Leu; the amino acid at position 245 is Arg; the amino acid at position 249 is Pro; the amino acid at position 250 is Gln or Glu; the amino acid at position 251 is Arg, Asp, Glu, or Leu; the amino acid at position 252 is Phe, Ser, Thr, or Tyr; the amino acid at position 254 is Ser or Thr; the amino acid at position 255 is Arg, Gly, Ile, or Leu; the amino acid at position 256 is Ala, Arg, Asn, Asp, Gln, Glu, Pro, or Thr; the amino acid at position 257 is Ala, Ile, Met, Asn, Ser, or Val; the amino acid at position 258 is Asp; the amino acid at position 260 is Ser; the amino acid at position 262 is Leu; the amino acid at position 270 is Lys; the amino acid at position 272 is Leu or Arg; the amino acid at position 279 is Ala, Asp, Gly, His, Met, Asn, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 283 is Ala, Asp, Phe, Gly, His, Ile, Lys, Leu, Asn, Pro, Gln, Arg, Ser, Thr, Trp, or Tyr; the amino acid at position 285 is Asn; the amino acid at position 286 is Phe; the amino acid at position 288 is Asn or Pro; the amino acid at position 293 is Val; the amino acid at position 307 is Ala, Glu, Gln, or Met; the amino acid at position 308 is Ile, Pro, or Thr; the amino acid at position 309 is Pro, the amino acid at position 311 is Ala, Glu, Ile, Lys, Leu, Met, Ser, Val, or Trp; the amino acid at position 312 is Ala, Asp, or Pro; the amino acid at position 314 is Ala or Leu; the amino acid at position 316 is Lys; the amino acid at position 317 is Pro; the amino acid at position 318 is Asn or Thr; the amino acid at position 332 is Phe, His, Lys, Leu, Met, Arg, Ser, or Trp; the amino acid at position 339 is Asn, Thr, or Trp; the amino acid at position 341 is Pro; the amino acid at position 343 is Glu, His, Lys, Gln, Arg, Thr, or Tyr; the amino acid at position 375 is Arg; the amino acid at position 376 is Gly, Ile, Met, Pro, Thr, or Val; the amino acid at position 377 is Lys; the amino acid at position 378 is Asp, Asn, or Val; the amino acid at position 380 is Ala, Asn, Ser, or Thr; the amino acid at position 382 is Phe, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, Trp, or Tyr; the amino acid at position 385 is Ala, Arg, Asp, Gly, His, Lys, Ser, or Thr; the amino acid at position 386 is Arg, Asp, Ile, Lys, Met, Pro, Ser, or Thr; the amino acid at position 387 is Ala, Arg, His, Pro, Ser, or Thr; the amino acid at position 389 is Asn, Pro, or Ser; the amino acid at position 423 is Asn; the amino acid at position 427 is Asn; the amino acid at position 428 is Leu, Met, Phe, Ser, or Thr; the amino acid at position 430 is Ala, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Gln, Arg, Ser, Thr, Val, or Tyr; the amino acid at position 431 is His or Asn; the amino acid at position 433 is Arg, Gln, His, Ile, Lys, Pro, or Ser; the amino acid at position 434 is Ala, Gly, His, Phe, Ser, Trp, or Tyr; the amino acid at position 436 is Arg, Asn, His, Ile, Leu, Lys, Met, or Thr; the amino acid at position 438 is Lys, Leu, Thr, or Trp; the amino acid at position 440 is Lys; the amino acid at position 442 is Lys.
 69. The method of claim 54, wherein the antigen is High Mobility Group Box 1 (HMGB1).
 70. The method of claim 69, wherein the antibody blocks the binding of HMGB1 to Receptor for Advanced Glycation Endproducts (RAGE) or Toll-like receptor 4 (TLR4).
 71. The method of claim 69, wherein the condition is sepsis.
 72. The method of claim 54, wherein the antigen is Connective Tissue Growth Factor (CTGF).
 73. The method of claim 72, wherein the condition is fibrosis.
 74. A method of reducing the concentration of an antigen in the plasma of an individual, the method comprising identifying an individual whose plasma comprises the antigen and administering an antibody that binds to the antigen, wherein the antigen has two or more physiological activities, and wherein the antibody comprises an antigen-binding domain as described in (a) below and an Fc region as described in (b) below: (a) the antigen-binding domain binds to the antigen and thereby inhibits a first physiological activity of the antigen but not a second physiological activity of the antigen, wherein the antigen-binding domain's antigen-binding activity varies with pH as described in (i) below, or with calcium ion concentration as described in (ii) below, or with both: (i) the antigen-binding activity is lower at a first pH in the range of 4.0 to 6.5 than at a second pH in the range of 7.0 to 9.0, wherein the ratio of (A) the KD value for antigen binding by the selected antigen-binding domain at the first pH, to (B) the KD value for antigen binding by the selected antigen-binding domain at the second pH (KD (first pH)/KD (second pH)) is 2 or more, (ii) the antigen-binding activity is lower at a first calcium ion concentration in the range of 0.1 uM to 30 uM than at a second calcium ion concentration in the range of 100 uM to 10 mM, wherein the ratio of (A) the KD value for antigen binding by the selected antigen-binding domain at the first calcium ion concentration, to (B) the KD value for antigen binding by the selected antigen-binding domain at the second calcium ion concentration (KD (first calcium ion concentration)/KD (second calcium ion concentration)) is 2 or more; and (b) the Fc region: (1) has an amino acid sequence that is not identical to the sequence of an Fc region of any native human IgG, (2) binds a FcRn at a pH in the range of 4.0 to 6.5, and (3) at a pH in the range of 7.0 to 9.0, binds to a human Fc receptor with affinity greater than the affinity with which any native human IgG binds to the human Fc receptor. 